Newly arrived at Cambridge, Maurice Hall meets Lord Risley at a luncheon in the Dean's office. Risley invites Hall to visit him in his rooms, to continue their conversation. On the way, Hall practices greeting Risley as he walks through the corridors, to the amusement of some passing students. When he arrives, Risley is not there. Instead, Hall encounters an older student, Clive Durham.

While the attraction between the two soon takes a physical turn (in the form of horseplay), Clive, who mocks the Dean for asking students to omit references to the "unspeakable vice of the Greeks" during a classical translation, stresses that he doesn't advocate the physical act of masculine love.

The Dean sees Maurice and Clive riding off into the countryside together, when they have finally admitted their feelings for each other. Embracing in the long grass, Clive rebuffs Maurice's sexual advances. Even a kiss, he believes, will bring them down and spoil everything.

Clive leaves Cambridge after refusing to apologise for missing one of the Dean's lectures. His decision to abandon his degree in favour of working for his late father's stockbroking firm angers family friend, Dr Barry.

While Maurice works and Clive studies, their affair continues, albeit platonically, until Lord Risley's arrest for indecency changes things forever. Clive, who refused to offer his friend a testimonial in court, collapses at a graduation dinner in his honour. He goes to Greece to recuperate and, upon his return, announces to Maurice that they both must change. Soon after, Clive gets engaged.

Maurice is beginning to fall apart, so confesses his "secret trouble" to Dr Ross, who scoffs at the suggestion of homosexuality but recommends he see a hypnotherapist. Despite being open to aversion therapy, Maurice cannot shake his desires - even after taking the doctor's advice and returning to the country to "stroll around with a gun".

When gamekeeper Alec Scudder climbs through his window, Maurice ceases to be open to the therapist's heterosexual suggestions. He begins though, to fret about being blackmailed; Scudder has invited him to rendezvous at the boathouse.

Maurice's reaction when Scudder visits his office, demanding to know why he didn't come, leaves the young servant so humiliated he almost does attempt blackmail. The situation is however resolved, and the pair spend the afternoon together, in a rented room.

When Maurice asks Alec to abandon his plans to travel to The Argentines, Scudder says that would be the ruin of them both. Yet, when Maurice goes to bid the ship farewell, Alec is not on board.

Back at the country house, Maurice tells Clive about his relationship with Alec, whom he then joins at the boathouse. Clive gazes out into the rain, thinking about Maurice as his wife rests her head on his shoulder.