Edgar G. Ulmer's Detour begins in a diner somewhere in the middle of nowhere as Al Roberts (Tom Neal) ruminates in voice over about his life and what has lead him to this place in time. He's got a tale to tell and there's a reason because it has taught Al something about fate. His experiences have left Al irascible and he argues sullenly with the waitress, the diner manager and a trucker who drops a nickel in a jukebox and plays the song that Al and his girlfriend called their song. Al's problem becomes more apparent as he explains the events that have brought him here. In flashback, he talks about his relationship with his singer girlfriend Sue (Claudia Drake) as he accompanied her on piano in a New York club. When she leaves for fame and fortune in Los Angeles, Al is lonely and decides to hitchhike to the coast to be with her. He accepts a ride from good-time-Charlie Charles Haskell Jr. (Edmund MacDonald). During their drive Haskell tells Al a little about himself, relating a story about deep scratches he has on his hand that he received when he picked up a woman who shunned his advances. When Haskell suffers an attack and dies, Roberts, fearing that he will be accused of murder takes on the man's identity and begins driving the car himself. At a gas station, Al picks up Vera (Ann Savage), who blurts out, "Where did you leave his body?" It turns out that Vera had accepted a ride from Haskell earlier and she is the one who has given him the scratches on his hand. Threatening to summon the police, Vera forces Al to pose as Haskell in order to collect an inheritance from the man's millionaire father. During their time together Vera causes another problem to befall Al and fate to intervene.