"The Dresser" opens with a performance of "Othello" at a regional theater in England during the last days of World War Two. In the title role is an ageing, once-famous Shakespearean actor identified to us only as "Sir" (Albert Finney). He is of the old. bombastic school of British acting, full of grand gestures and fine oratory. As the curtain comes down on the last act, and as the actors line up for their curtain call, Sir lectures them on the mistakes they've made during the performance, showing us that he is the leader of this traveling band of actors bringing Shakespeare to the provinces during wartime.
Waiting backstage is Norman (Tom Courtenay), who has been Sir's dresser for decades. Norman is an efficient, somewhat effeminate little man who knows Sir's every whim and fancy, is used to his tirades and temperamental rants and is, for all intents and purposes, Sir's servant. As Norman waits for Sir to come offstage after a typically florid closing address to the audience, we see one way he copes with his job as he takes a nip from a handy little bottle of brandy always in his back pocket.
Next we see the company hurrying to its next venue, a theater in the industrial town of Bradford where Sir is to give his renowned portrayal of King Lear. The train nearly leaves without them, as Sir makes his stately progress through the train station to the platform, Norman scurrying ahead to plead with the train guard the even the conductor to hold the train for Sir's arrival. But the train begins to pull out of the station, until Sir delivers a loud, commanding "STOP....THAT....TRAIN!" from the platform steps. The conductor, taken aback, does just that and Sir placidly leads his company aboard.
Arriving in Bradford, however, we soon learn another source of Norman's anxiety, for it becomes obvious that Sir's mental capacities are rapidly fading. Norman rescues him from a confused, almost violent rant in the town square that lands Sir in the hospital. As the company tries to decide what to do, Sir unexpectedly arrives at the theater, disoriented and exhausted, saying he's checked himself out of the hospital. Norman ushers Sir theater's dressing room, fiercely resisting the stage manager's insistence that the show be canceled and insisting Sir will be ready to go on.
The middle section of the film takes place nearly entirely in the dressing room, as Norman struggles to prepare Sir for the curtain. Sir's wandering mind and nearly incoherent ramblings gradually become more focused as Norman gets him to concentrate on applying his makeup, remembering his lines; and we see how dependent the two men are on each other. Sir would have no career left without Norman; Norman, even worse, would have no life without Sir, to whom he has so long dedicated all his time and energy. By the time Sir's wife, referred to only as "Her Ladyship" and who is playing Cordelia to her husband's Lear, arrives in the dressing room for the five-minute call, Sir is ready for the role we learn he has performed 227 times.
The curtain rises for the opening dialogue among Lear's courtiers, but Sir seems to mentally drift away while waiting for his cue, much to Norman's distress, forcing the hapless actors on stage to improvise speeches while Norman struggles to convince Sir of his entrance. Air raid sirens sound, signaling the possibility of an airstrike; and, indeed, distant bombs that can be heard falling seem to rouse Sir and he strides on stage to deliver what all agree is his finest portrayal of Lear in his long career.
After the triumphant performance, however, Sir collapses from exhaustion and Norman helps him to his dressing room to lie down. Sir requests Norman to read from an autobiography he claims to have been writing. Although all Sir has written is the opening dedication, Norman reads aloud Sir's gracious thank yous to his audiences, his fellow actors, to Shakespeare, to stage technicians...but not a word about his dresser who has served him so long and loyally. About to protest, Norman discovers that Sir has died while he's been reading. Norman, by now slightly drunk from the evening's brandy nips, flies into a rage, accusing Sir of being a thankless old sod, and in his anger even madly scribbles an addition to Sir's writing thanking himself. But Norman's anger only temporarily covers his disorientation at losing the only life he has known for so many years and, as Norman tearfully admits, the only man he has ever loved. The film closes with Norman sprawled across Sir's body, unwilling to let go of his life and his love.