A group of elderly people are giving interviews about having lived in a climate of crop blight and constant dust reminiscent of The Great Depression of the 1930's. The first one seen is an elderly woman stating her father was a farmer, but did not start out that way.
The scene changes. We are introduced to a farmer and widower named Joe Cooper (Matthew McConaughey). He is a college-educated former NASA test pilot and engineer who was forced to give up his occupation to farm, living in a run down farmhouse, presumably owned by his father in law. They farm corn, with wheat no longer available and okra just now having become extinct due to blight. We see no animal life.
It is the 2060's in eastern Colorado. More than half the world's population has been decimated from famine and America has been reduced to a struggling agrarian society for the past 30 years. Technology has come to a standstill for the past 40 or so years, with automobiles no longer produced and a computer laptop is a luxury item. There is no military or wars anymore. At a certain age, kids are tested to determine what occupations they will have to take to help humanity survive. In school, it is taught that the US going to the moon in 1969 was a hoax to drive the Soviet Union into bankruptcy and win the Cold War.
Cooper's family consists of his 65-year-old father-in-law, Donald (John Lithgow),15-year-old son Tom (Timothée Chalamet), and 10-year-old daughter Murph (Mackenzie Foy). Donald was born at the end of the 20th or beginning of the 21st century and fondly recalls times when technology was constantly changing and new gadgets being invented. He is a down-to-Earth man who takes care of the household duties and gets along well with Cooper. The two of them sit on the porch drinking beer in the evening and philosophize about the condition of the world and how things should be. Joe's son Tom is a boy of average intelligence already being ruled out to be a farmer by the school administration, since a college education is now something only a very small percentage those will enjoy the privilege of. His daughter Murph is a feisty and highly intelligent girl whom Cooper is very close to and who shares his affinity with space and science. She believes her room is haunted by a ghost because books keep falling off her shelves and a lunar ship model was just knocked over.
The Cooper family lives a pretty simple life and have a rare treat of attending a game of a supposedly major league baseball team at a local ball field similar to what the little league play on today. His father in law is unimpressed at the amateurishness of the players and having only popcorn for refreshments and no hot dogs. An approaching dust cloud interrupts the game reminding them of the grim world they live in, and ends it prematurely. The Cooper family makes back to the farmhouse during the dust storm and Murph's bedroom did not have the window closed and the dust settled into perfect lines on the floor. Cooper spends the entire night studying the lines and Cooper thinks the lines are binary code and coordinates for a place he feels the need to find and uses a map. He spends the next day driving to the Rockies and his daughter sneaks into the truck to come with him.
Soon after arriving at his final destination, Cooper is apprehended and tasered into unconsciousness by a strange looking robot called TARS. It turns out he is in the best-kept secret in the world, a bunker, and meets his old boss from NASA, an Englishman named Dr. John Brand (Michael Caine), plus his beautiful young daughter, Amelia Brand (Anne Hathaway). Nobody is convinced that Cooper just stumbled into the place by accident and Dr. Brand believes a force brought Cooper there. The compound Cooper found is actually the remnants of NASA, inhabiting the facility in secret and no longer funded by the government because of the scarcity of resources. There is a space mission leaving soon to go through a wormhole of unknown origin near Saturn that will take them to three potentially habitable planets, two of them orbiting a supermassive black hole named Gargantua; a large black sphere about the size in diameter of Earth's sun but which has a solar mass of about 50 million Earth suns. Ten years earlier, 12 individual astronauts were sent out through the wormhole in 12 different ships, but only three (Miller, Mann, and Edmond's) activated the thumbs up beacon, all of whom are at three planets. At the moment, NASA has nobody to pilot the spacecraft and at the last minute they want Cooper to go, despite his family responsibilities.
The bunker itself is actually a centrifuge, which is projected to become something else later on. The mission has two plans: Plan A is to get the centrifuge into orbit as a space station and rescue a large number of people; this requires Dr. Brand to solve the equation that will allow the scientists to overcome gravity and get the centrifuge into orbit. Plan B is to colonize the most habitable of the three planets along with a bunch of frozen embryos to repopulate the species. Dr. Brand assures Cooper the Earth is dying and humanity doesn't have much longer and that he needs to pilot the craft and explore, lest his family and the rest of the world all die soon. Cooper is very reluctant, because he's barely left Earth's atmosphere, but Brand reassures Cooper the twelve astronauts sent on the mission never even left the simulators beforehand.
The next day, Cooper and Murph return to the farmhouse, his daughter is extremely upset with him for choosing the mission. That night Cooper and Donald are sitting on the porch drinking beer and Cooper reminding Donald once again of the futility of staying and the conditions they live in. Donald assures Cooper he's doing the right thing, but needs to set things right with Murph. The next morning, Cooper does his best to comfort a sobbing Murph and promises to come back to her and that they might even be the same age when he returns, giving her a wristwatch to compare time. Murph refuses his assurance and that her bookshelf is communicating with her in Morse Code to "stay". Despite her pleas, Cooper won't back down and one more book falls down before he leaves, but Cooper disregards it. Cooper leaves and says goodbye to Tom and Donald and while he's driving away, Murph storms out the front door wanting to see him one last time, but it's too late.
The space shuttlecraft rockets away from Earth at high speed with Cooper, Amelia Brand, Dr. Doyle (Wes Bentley), Dr. Nikolai "Rom" Romilly (David Gyasi), and the TARS and CASE robots on board. Doyle and Romilly are two scientists that were in the conference room at NASA during the meeting with Cooper. When the spacecraft leaves the atmosphere, everything goes quiet all of a sudden, except the inside. The ring shaped Endurance is up ahead and they dock with it, which has all their needs for space travel. The Endurance is leaving Earth and they bid farewell to a spinning Earth and have to look forward to the lonely, claustrophobic, and potentially dangerous reality of space and put themselves in a plastic-covered water cryosleep bed for the two-year journey to Saturn.
Dr. Brand makes a trip in Cooper's old 2010 Dodge ram truck to deliver the vehicle back to the homestead and give a tape recorded message from Cooper to his family. Murph appears hoping her father is home, but angrily storms back into the house. Donald tells Dr. Brand about how Murph is making fools out of her teachers, but Brand tells Donald maybe she'll eventually make a fool out of him.
Two years later: the Endurance is orbiting Saturn and Cooper is out of cryosleep, reviewing video messages. His son Tom tells him he's doing okay and Donald says hi, telling Cooper that Murph still refuses to talk to him. The Endurance crew come upon the wormhole, which resembles a plasma globe and will provide a quick channel for the crew to reach the three planets in the next galaxy. The crew take off for the rough ride, (a la 2001 infinity) and come to their first mission, Miller's Planet. During the time through the wormhole, Amelia reaches out and feels she touched someone's hand.
They find themselves in a region of space around 10 billion light years from planet Earth. They decide to head first to Miller's planet, intending to stop there only briefly as its close proximity to Gargantua causes severe gravitational time dilation with each hour spent on the surface costing seven Earth years. Cooper, Amelia, Doyle, and the robot CASE decide to risk themselves and intend to be in and out of there in just minutes to survey while Romilly remains on the Endurance to study the black hole and get quantum data from it. When they land, all they find is shallow water and wreckage of Miller's ship, who apparently died and had arrived just an hour or two earlier, even though she sent the thumbs up beacon on Earth 10 years before. The crew think there are mountains in the distance that turn out to be giant tsunami waves. Brand becomes trapped under the Miller wreckage and has to be rescued and carried back by CASE, Doyle is drowned, and the ship is flooded and won't be able to make it out for another hour, costing them years. Cooper is frustrated at Brand, but forgives her mistake. After the engines are mostly emptied of water, Cooper fires them up and just manages to escape the next tidal wave and fly off the surface.
Cooper and Brand make it back to the Endurance to find an aged and gray Romilly in a robe -- 23 Earth years have passed and Romilly has spent most of the time waiting with a couple of stretches in cryosleep. It is now about the year 2090 on Earth. They are all beyond crushed, but Brand is relieved to know her father is still alive and well. They are receiving messages from Earth, but unable to transmit out. Cooper reviews all the videos and breaks down looking at 23 years of recorded videos and sees before his very eyes his 17-year-old son Tom showing a picture of what he believes is the right girl for him. In the next video, Tom (now played by Casey Affleck) introduces to Cooper to his grandson Jesse. In the next video, a now beaten and 40-year-old Tom reveals that Donald died a week ago and is buried next to Jesse and that he believes Cooper to be missing or dead and needs to let him go. Then afterwards an apparent live recording comes from Murph (now played by Jessica Chastain). After 25 years of silence, a still stubborn and saddened Murph tells off her father for not fulfilling the possibility of being back because she is now 35 years of age, which is the same age he was when he left Earth. It's like a knife has been plunged into his heart and he feels he has betrayed her badly and has no way to communicate back with her.
On Earth, Murph stops recording the video. She is now working for Dr. Brand and living in the NASA bunker, who is now about 90-years-old and confined to a wheelchair. Brand is still trying to solve the incomplete gravity equation to get Plan A rolling and is reassuring Murph that the crew of the Endurance are receiving their recorded messages, but the crew can't transmit out.
Now that the Endurance crew have recovered emotionally from Murph's video, they debate whether to visit Mann's planet or Edmond's planet, because they only have enough fuel to visit one of them before they head back to Earth. Brand wants to visit Edmond's Planet because his planet appears to be the better prospect, but Cooper wants to visit Mann's because he's still transmitting his beacon.
On Earth, Murph returns to the old Cooper homestead with her brother Tom, a farmer. He has just torched a third of his crop because of blight, which is spreading. He now has his old neighbor's crop to cultivate since the neighbor moved or died. They believe the farm will soon produce nothing. She has dinner of corn soufflé and corn-on-the-cob with Tom, his wife Lois (Leah Cairns), and son Coop. She discovers Coop has a bad cough. They want her to stay the night, but she refuses because of bad memories from her childhood. Murph is aware that the nitrogen levels in the air are taking their toll more and more each day on their son.
A day or two later, Murph is back at the NASA bunker and learns Dr. Brand is dying. He confesses to her that Plan A is not possible and that he had lied to her. He could never solve the gravity equation to get people off Earth. She believes her father knew all about Brand's scheme and that he escaped and purposefully left her and everyone else to die. Dr Brand dies. Murph sends a video message to Amelia informing her of her father's death and begs him to tell the truth that the whole thing had been a sham.
The Endurance crew make it to Mann's Planet a few months later; the planet is perpetually cold, covered with glaciers, and has a poisonous atmosphere of methane filled with ice clouds. Dr. Mann (Matt Damon), who has been in cryosleep for over 35 years, is awakened by Cooper and has a mental breakdown and relieved he is rescued. He tells the story of the frigid, but beautiful world he lives in, indicating it has 80% of Earth's gravity and a lower part is livable, possibly even a source of fresh water.
Brand sees the video Murph sent about her father dying and Plan A being a sham. She is absolutely shocked and had no idea, but Mann reassures her the equation was actually solved long ago and determined to be impossible before he ever went on the mission. The only way to ever get data would be to get inside a black hole, which is impossible without being killed.
Back on Earth, Murph and her boyfriend, Dr. Getty (Topher Grace), another NASA physicist, are driving in her Jeep through the bleak plains surveying the endless clouds of black smoke and families with their decrepit 80-90 year old vehicles on the road with their belongings in tow, much like Midwestern farmers in the 1930's escaping to go west to find a better life. She knows the equation is solvable as long as it comes from a black hole and that Dr. Brand only gave part of it. Somewhere in her subconscious, she has a gut feeling that the coordinates of dust on the floor of her bedroom long ago gave her a hint, along the books being pushed off the shelf, and with the Morse code message for Cooper to "stay". She has a feeling this "ghost" is a being that has tried to comfort her and help save humanity. She knows it's not the end and that humanity is running out of time.
Simultaneously, Mann is showing Cooper the icy and forbidding world. Murph is back at the Cooper homestead with Dr. Getty examining Tom's son for his lungs. Dr. Mann pulls off Cooper's voice beacon and pushes Cooper off the cliff and Murph's brother Tom is outraged by Dr. Getty's comment that they can't stay and will die, hitting him in the face. Mann reveals to Cooper that the planet is uninhabitable and that he sent the signal so he could take Cooper's spaceship to return to Earth. Murph confronts Tom that her father never meant to save them, but escape and leave it up to her and Tom outright refuses and tells her to leave, believing it's his duty to take care of the farm to fulfill his promise for his father. Mann is trying to kill Cooper by breaking his helmet's visor, allowing the ammonia-rich air to suffocate Cooper.
Cooper manages to reach his voice beacon that was taken off of his helmet by Mann to call out for Brand to rescue him. Murph and Dr. Getty are driving back to NASA, but in a fit of rage, she pulls over and pours gasoline over corn crops and sets them on fire, in order to distract Tom and get back to the farmhouse. Cooper has been rescued by Brand. Mann's living quarters on the planet has exploded and Romilly killed. Romilly was killed because he was trying to retrieve data from Mann's robot KIPP, which was booby trapped and supposed to reveal the truth about the planet. TARS comes out of the rubble to be rescued by Cooper and Brand and they leave the planet.
On Earth, Tom's family is now out of the house and Murph is now in her old bedroom trying to make sense of the past. Cooper and Brand are leaving the planet, but Mann is also in another shuttle trying to do so and refuses to listen to their pleas to not attempt to dock with the Endurance. Murph is in her bedroom examining her old belongings to find out what the "ghost" might be telling her.
Dr. Mann has steadfastly refused to listen to the warnings from Cooper and Brand not to dock with the Endurance, but he continues his efforts. He's manually maneuvered the ship into docking position, but ignores the computer's warnings of "imperfect lock" and we see the docking pincers attempting to grab but failing to lock in. In mid-sentence the coupling release and the violent expulsion of air into space carries him with it, and resulting collision causes an explosion. The Endurance is now out of control and Cooper tells Brand that he is going to dock with it, even though it is now in a rapid rotation. Though the centrifugal g-forces from the spin are enormous, Cooper is able to dock. However, they are unable to get back to Earth and have to go to Edmond's Planet to even hope to survive, because of the life support being destroyed. They have to slingshot around the black hole Gargantua in order to make it to Edmond's Planet and on manual controls.
During the harrowing orbit around Gargantua, Cooper and TARS detach their respective shuttles and get sucked into the black hole, sacrificing themselves to collect data on the singularity, and propel Amelia and CASE faster by reducing the ship's mass. Cooper separates from Brand in his Ranger, without her prior knowledge, and Brand is on a path that will take her to Edmond's Planet. He realizes the cost of orbiting the black hole due to the gravitational time dilation will be 51 Earth years, but takes the chance. Brand is outraged with Cooper and now left alone with CASE.
As Cooper's shuttle falls into the black hole, gravitational forces begin to rip it apart. Cooper is descending towards the center of the black hole with pellets that look like sleet hitting his Ranger spaceship. The computer of his ship tells him to eject himself and without reluctance, he does it.
Cooper descends in the black hole towards a grid full of cubbyholes thinking he's dead and finds himself in some sort of afterlife and unaware of what sort of surroundings he's in which resembles a tesseract. He hits an object along with a bunch of others that look like books stacked and knocks one down, revealing ten-year-old Murph reacting at an object falling from her bookshelf back at the farmhouse. He knocked down the lunar lander model shown at the beginning of the movie. He's screaming out for Murph, but she walks away with it and doesn't hear him. Then he sees Murph in another part of the grid pleading for her father not to leave. Cooper watches this begging himself not to go and to stay using Morse Code by knocking the books off the shelf. Cooper breaks down realizing that he should have listened and not gone on the mission. Then there is adult Murph at the bedroom while the fire is still burning and she realizes all along that her father himself was the ghost communicating with her feeling comforted and reassured. Now it's all making sense to her and she's no longer angry with him and has hope. But she's still trying to find out what her father is trying to signal to her, recalling the events of the dust storm coordinates and the books falling off.
TARS gets Cooper out of his grief-stricken state that he survived and tells Cooper that some fifth dimensional beings sent him there to communicate with Murph and that his love for his daughter sent him there to help her. Cooper is delighted to see TARS is there with him. Cooper realizes that the mission was not a mistake and that he will get done what he needs to. Murph has been the chosen one to save humanity, but Cooper is the one chosen to help engineer it. He sends the coordinates to himself at the farmhouse to NASA, then the data from the black hole through TARS via Morse Code to a wristwatch he gave Murph before he left, which is the gravity equation. Preteen Murph put the watch back on the shelf making it possible for Cooper to add the black hole equation to it. Adult Murph picks up the old wristwatch out of a box of her old keepsakes seeing the second hand with the Morse Code realizing it's the key. Dr. Getty is pleading with Murph to get out and for them to leave because the fire is out. Murph leaves the farmhouse with the watch in her hand, and angry Tom returns, but she tells him about the watch, embraces him assuring her father was the ghost all along and will save them. Tom is befuddled by it all, but accepts her hug.
Murph returns to the NASA bunker and completes the equation using the data from the wristwatch. She writes it all down, and throws the papers off the deck of the centrifuge under construction that the equation is solved. She kisses Dr. Getty in a fit of happiness. So what's going to happen soon might save most of remaining humanity.
Back in the black hole, the tesseract is now closing up, with Cooper convinced it all worked and Cooper is comforted that future human beings constructed it to make all this happen and tells TARS everything is okay. He comes across the Endurance when it passed through the wormhole and touches Brand's hand, then knocked unconscious into the orbit of Saturn with a couple of beaming lights approaching him.
Cooper wakes up to find himself in a hospital bed. A very clean room with background noise of a baseball bat cracking a ball and birds chirping. A doctor tells him to take it easy jokingly telling him he is now 124 years old, but he still looks the same in his mid to late 30s. The doctor tells Cooper he's very lucky to be alive because space rangers found him with only minutes left in his oxygen. Cooper looks outside the window of his room with kids playing baseball with a batter hitting a ball into the sky, which turns out to be the skylight of an upside down house with kids cheering at the window being broken. Cooper is told he's on Cooper Station orbiting Saturn and thinks the station is named after him, but it was named after his daughter Murph. She's still living and on another space station and will be there to visit him in a couple of weeks despite her age and health. Cooper is delighted that Plan A did indeed work out and that the gravity equation was solved. The very centrifuge that was the NASA bunker is now a space station to sustain human life.
Cooper is now released from his hospital room by a tour guide and shown the station, an O'Neill cylinder with a old world rural American environment and has artificial sunlight beaming from one side, which was the same place the rocket took off from 89 years ago. They pass by a group of sleek ranger ships that are more efficient than what he used and he takes a great interest in them. He is led to a museum exhibit, which is his old farmhouse, only much cleaner and restored. There are videos all over the place of elderly people telling of the dust bowl they lived in, whom you saw at the beginning of the movie, one of which is his daughter. He finds a shorted out TARS in the farmhouse the rangers recovered and immediately repairs him.
Cooper is sitting on the front porch that "night" with TARS drinking beer like he and Donald used to do, but very dissatisfied at the artificial surroundings and pretending to be home. He's more interested in the spaceships than anything else and still yearning to explore the unknown. Plus almost everybody he knew is now dead and he wasn't welcomed back as a hero.
Cooper is about to go to the hospital room where Murph (now played by Ellen Burstyn) is living out the final days of her life -- she'd insisted on being brought to the station to say goodbye to her father. A nurse tells Cooper that her family is in there and that she's spent the last two years in cryosleep. He wasn't aware she had a family and carefully opens the door with over a dozen people, from small children to middle aged adults surrounding her bed. His grandchildren, great-grandchildren, great-great-grandchildren, and their spouses are there, yet he pays no mind to them while they are puzzled by his appearance. His main interest is seeing his daughter. Murph breaks down in delight at the sight of him, and he takes her hand without any reluctance or awkwardness, even though he's the same age he was when he left and she's 99 years old and near death. He assures her he was the ghost that communicated to her in her room and she already knew for years even though nobody believed her. He tells her he's now here for her, but in her still feisty and stubborn ways, she doesn't want him to see her die, saying her kids are here for her and that she forgave him and made peace with his disappearance decades ago.
Cooper slowly leaves her room to see her one last time and she's surrounded by her beloved family and his descendants he knows nothing about. Knowing the space station is not where he belongs, he takes Murph's advice to go seek out Brand, who has landed on Edmond's Planet to start colonization. It is a desolate place resembling Mars, but the air is breathable and can sustain life, so it's the best humanity can do outside the space stations. Edmonds died long ago and is buried by CASE, but she continues to set up camp and puts herself in cryosleep. Cooper steals one of the new generation ranger ships he's been obsessed with and goes with TARS through the wormhole to find her and beat the rangers at their mission.