Wet mucus, hot venom, undigested rage, and prickly memory are among the many ingredients in the phantasmagoric stew of Dennis Potter’s The Singing Detective. Not to mention an abiding affection for Duke Ellington and Ella Fitzgerald. Originally broadcast on British television in 1986, the six-part series aired on PBS in 1988, and since then it’s elicited more critical superlatives than just about anything else that’s ever been made for TV. Now that it’s arrived on DVD (from BBC Video), viewers can see that it gets only better with time.

Phantasmagoric is as good a word as any to describe a story that — though it involves dozens of characters, a handful of musical attitudes, and at least three dramatic genres — takes place almost entirely in one man’s head. Philip E. Marlow (Michael Gambon) is the author of a hard-boiled detective novel about a 1940s era gumshoe who spends his down time crooning pop standards in nightclubs. He’s also our tour guide in and around his painfully injured body and soul. We accompany him as he revisits his devastated health, his crumbling marriage, and his stark and disrupted childhood in the Forest of Dean, a mining town on the Welsh border.

To the sound of a lone harmonica playing "Peg o’ My Heart," the story opens as a trenchcoated figure drops a coin into the hands of a beggar standing in the shadows of a London street. Wrapped around the coin is a piece of paper with the word "Skinscapes." The man in the trenchcoat then walks into a nightclub called Skinscapes, where a singer is performing "I’ve Got You Under My Skin." The camera cuts to a modern-day hospital ward where a hideously disfigured patient is returning to his bed. We learn that Marlow is being treated for psoriatic arthropathy, a disease that cripples his joints and makes his skin peel.

The product of Potter’s fearless writing and Gambon’s unsparing performance, Marlow is rawer and more abrasive than most characters on the big screen, never mind the small one. (It would take 10 each of NYPD Blue’s David Milch and Dennis Franz to come even close.) His existence is wrapped up in defending himself against the dehumanization of the hospital ward, the powerlessness brought on by his illness, and the sexual humiliation he imagines. He braves the condescension of doctors and nurses by spewing forth unrelenting bile — which is ignored by those listening. Is it any wonder that he begins to hallucinate?

Before you quite catch on, the quizzical doctors circling Marlow’s bed are transformed into a natty quartet singing "Dem Bones" — or, rather, pantomiming as the voices of Fred Waring and the Pennsylvanians come out of their mouths. The entire ward dissolves into a Broadwayesque musical production number whose upbeat tone and energy run deliciously counter to the preceding glumness. This breathtaking juxtaposition of dark and light is the pattern that weaves through The Singing Detective. "Accentuate the Positive," as sung by Bing Crosby and the Andrews Sisters, comes out of the throats of cloying Christian proselytizers in a Sunday-morning hospital ward. A carload of grizzled soldiers sing "Paper Doll" in the voices of the Mills Brothers.

Potter died in 1994, of pancreatic cancer rather than the skin disease he shared with his protagonist. By the mid ’80s, the writer was well known on the BBC for such mini-series as Blue Remembered Hills and Pennies from Heaven, the source of the 1981 Steve Martin movie. With The Singing Detective, his greatest work, Potter embraces both the ugliest parts of human nature and the delectable joys of life, without so much as one unearned sentimental blink.

Besides dramatizing a character’s unforgettable journey from despair to hope, The Singing Detective also boasts one of the best casts ever assembled, with the inimitable Bill Paterson as Marlow’s psychiatrist, Joanne Whalley as his nurse, Patrick Malahide as his nemesis, Janet Suzman as his wife, and Alison Steadman and Jim Carter as his parents. The series is made for the DVD format, which allows you to pause and dissect. This edition offers a documentary on Potter and a separate interview with him as well as less-than-revelatory commentary by director Jon Amiel and producer Kenneth Trodd. There’s virtually no information on the design or the filming of the production numbers. But what counts here is the work itself, which casts a long shadow over the landscape of TV’s current reality shows. Many viewers driven by a thirst for narrative will prefer Potter’s reality.