Almost twenty years ago the British writer Dennis Potter created a television story called "The Singing Detective," which ran as an eight-hour miniseries on the BBC, and later in the United States on PBS. Michael Gambon was Philip Marlow, a writer of detective pulp fiction who's cursed with a case of psoriasis so afflicting that his life is now defined only by pain, and he is confined to a hospital bed. As he lies there almost paralyzed, he creates a complex fiction, which we see on screen, in which versions of his life and childhood are dramatized as a detective story, with characters both contemporary and in fantasy - hospital doctors and nurses among them - breaking into song and dance from hits of the 1940s. The series was an amazing departure from conventional television, both a liberating creative achievement and a powerful experience for us in the audience. We had never seen anything quite like it before.

Potter was writing about himself: he suffered agonizing psoriasis, and ultimately died, in 1994, of a related cancer. Before he died, though, he wrote a screenplay of "The Singing Detective" which has now been made into an American movie. It stars the brilliant actor Robert Downey, Jr. as the pulp detective writer Dan Dark, also cursed with psoriasis and confined by his pain to a hospital bed, where only his mind and its fantasies can move freely. The fantasies are classic noir, with snap-brim hats, mustaches, slinky dresses, and revolvers figuring strongly. (Potter changed those fantasies and the songs and dances from the forties to the fifties, a better decade for American popular songs.) They are the means by which Dan can leave his bed and act out the stories he's writing in his head.

Dan has a wife, Nicola (Robin Wright Penn), who in those fantasies is cheating on him; she finds the draft of a screenplay and conspires with her lover to sell it without giving him credit. Perhaps she is, perhaps not. We can't tell the real from the imagined. There are flashbacks to his childhood, right out of "The Postman Always Rings Twice," in which his mother (Carla Gugino) cheats on his father with his ultra-virile young partner, at their godforsaken gas station in the desert; and then becomes a hooker in Los Angeles. And in the hospital Dan is wheeled reluctantly to his sessions with psychotherapist Dr. Gibbon (Mel Gibson in a wonderful performance of subtlety and modest manners - who knew he's bald?).

Downey sings, dances, investigates and rages in the film, without ever going beyond the utterly believable no matter the context. He is stalked by two hit men (Adrien Brody and Jon Polito), he has sexual fantasies about his nurse, and he resolves his most painful memories by letting them trigger another song, another dance, another episode in his detective thriller.