I have to admit I shifted uncomfortably in my seat the moment I saw a tap-dancing clown.

Apart from a guy wearing roller skates and a gorilla suit, I'm hard-pressed to think of a more groan-inducing theatrical trope. But The Unfortunates, running through April 10 at the American Conservatory Theater's Strand Theater, is so much more than that. It's a high-energy hallucination about the importance of maintaining your wits in the face of certain death (and to reveal but a minor plot point, the clown quickly dies of plague and joins a sort of Greek chorus of onlookers). A tent revival whose protagonist is a gambler with anger-management issues, it's derived from "St. James Infirmary," a blues ditty of unknown provenance. And as it detours through a plague-stricken village of the damned, The Unfortunates is a simple story about the hell of war that grows very complex indeed.

One prime virtue of Shana Cooper's production is that it puts to rest any notion of The Strand as an inferior sibling to The Geary, A.C.T.'s main theater. Between Riverside and Crazy, this season's opener, has a better-constructed narrative arc — it won Stephen Adly Guirgis the Pulitzer — but The Unfortunates' stagecraft is a wonder. This production maximizes all three axes, with some of the best dramatic exchanges emanating from the stage's outer depths, yet it never feels hemmed in by its surroundings. 

Rather, it's a delight to watch. In particular, the props and costuming, from Big Joe's enormous fists to the beaded wigs his deceased comrades wear to the red neon crosses that illuminate the proceedings, add a lurid streak to the fantasy. It's The Masque of the Red Death by way of wartime Mardi Gras, and Even Koko the occasionally tap-dancing clown turns out to possess dramatic heft.

There's one big sticking point, however. The Unfortunates is very quick — an hour and a half, no intermission — and gets to the main action with only a very quick intro, which seems like it could take place during World War II or be a figment of Big Joe's imagination. I was driven to distraction for much of the next hour wondering if Joe was dead and entering the underworld, if he was having a hallucination at the moment of death, if the play was set in the 1920s — and why, if the plague kills everyone, doesn't Rae have any arms? I get that The Unfortunates is a dreamscape operetta, but some crucial details feel tangled up.

But as the story unspools, that matters less and less as you inexorably give yourself over to the music. With his crooked, goofy grin, Ian Merrigan (Big Joe) is an affable protagonist, and virtually all the secondary cast members are winning, with powerful voices. The best performer, though, is Ramiz Monsef, who plays a variety of roles — most of them with a sinister cast, equal parts Joseph Goebbels and Judge Doom from Who Framed Roger Rabbit? A chilling amorality makes for the best demons, after all.

Although American theater lurches from crisis to crisis and always survives, a demographic time bomb looms. Audiences skew older, whiter, and more conservative than the general population, a fact which has proven stubbornly resistant to a great deal of soul-searching on programming. Now that Lin Manuel Miranda is firmly established as his generation's Stephen Sondheim — I really don't want to call him this generation's Andrew Lloyd Webber — hip-hop seems certainly to enter theater by capillary action. A few deep-pocketed septuagenarians would probably quibble with this assessment, but hip-hop is very well-suited to the stage and it's probably as good a way to get young patrons hooked on theater as any other. 

But The Unfortunates gets its musical cues from a much wider constellation of influences. There's gospel, New Orleans jazz, and songs that sounds like outtakes from Joe Cocker's version of "With a Little Help From My Friends," much of it sung by plague victims wearing beaked Arlecchino masks. Is the plague a metaphor for AIDS? The inevitability of death? The horror of war? The search for the answer, minor plot confusion and all, yields ambiguous results but also one of the best musical productions I've ever seen at A.C.T.; not even my father could fall asleep through this one. It never looked so fun to be incurable. 

The Unfortunates, through April 10, $45-$105, at the Strand Theater, 1127 Market, act-sf.org.