Gulley Jimson, an eccentric painter, is released from a one-month jail sentence for telephone harassment of his sponsor, Mr. Hickson, and is greeted at HM Prison Wormwood Scrubs by Nosey Barbon, who hopes to become his protégé. Jimson, wary of mentorship and the headaches of the art world, makes his way to his houseboat where his older lady friend Dee Coker has kept things running in his absence, a quiet orbit around his restless talent.
Desperate for funds, Jimson and Dee visit Hickson to secure payment for Jimson’s artwork. They also attempt to retrieve some works from Hickson’s place, but Dee intervenes and halts the theft. When Hickson phones the police, the two manage a narrow escape, slipping back into the margins of their precarious lives as artists.
Jimson responds to a note from A.W. Alabaster, secretary to Sir William Beeder and Lady Beeder, who are keen to acquire Jimson’s early pieces. The artist-and-friend duo then pursues a potential acquisition from Sara Monday, Jimson’s ex-wife, but she refuses to part with any of his earlier works, turning away their entreaties with a blunt insistence.
On a visit to the Beeders, Jimson spots a blank wall in their home and is suddenly inspired to paint The Raising of Lazarus. The Beeders depart for six weeks, granting him the room to work in relative privacy. An old artistic rival, Abel, intrudes with a large block of marble to fulfill a sculpture commission for British Rail, injecting a new pressure into Jimson’s already volatile scheme. Jimson pawns the Beeders’ valuables to fund his latest venture, and a mishap with the marble tears a hole in the Beeders’ floor, leaving both art and home damaged. After Jimson completes the painting, the Beeders return, shocked by the audacity of the piece and the gaping hole, and they tumble through it in their surprise.
Back at the houseboat, Dee reveals that Hickson has died and that his bequest includes Jimson’s own works, arranged to be shown “to the nation” at the Tate Gallery. Jimson visits the exhibit and, amid the long queue, spots Sara once more. She hands him a roll tube, but when he returns to the boat, Dee and Nosey discover that the roll contains only toilet paper. Nosey shadows Jimson to Sara’s house, where Sara is knocked unconscious as Jimson seizes the painting.
Seeking shelter in an abandoned church, Jimson feels the surge to tackle his greatest project yet, The Last Judgment, on a blank wall. Learning the church is slated for demolition within a fortnight, Jimson, Nosey, and Dee recruit local youths to help complete the mural and even enlist Lady Beeder to participate. As demolition looms, a council official objects, yet the makeshift team presses on, the mural rising in defiance of the clock.
On the scheduled day of demolition, the momentum of the work eclipses doubt, and Jimson makes a dramatic decision to protect the piece by destroying it himself, driving a bulldozer through the church wall to prevent others from finishing it in a way he cannot accept. He then makes his way back to his boat and sails down the Thames, pursued by Nosey and Dee who try but fail to halt him, leaving his grand, controversial vision to drift along the river’s current as he disappears into the distance.
