“John Dies at the End” is a horror-comedy that scores more points for trippiness than it does for truth in title advertising.

Before it trips over its own overly complex plot, before the comic leads have exhausted their modestly amusing repertoires, this odd stoner/ sci fi creature feature blows out of the gate and threatens — for about 30 minutes — to blow your mind.

Then it doesn’t.

John’s pal, David Wong (Chase Williamson), looks nothing like a David Wong. A reporter (Paul Giamatti) notices this. Dave “had my last name changed” to help him hide out. “Wong is the most common name in the world.”

Dave has reason to lay low. He’s on to something. And the tale he narrates to the mildly incredulous reporter is a doozy. Dave’s pal, the elusive John (Rob Mayes), stumbled into a drug that looks like soy sauce. “The Sauce,” which you have to inject, lets the user travel through space and time, to another dimension.

But when the users come back, many of them aren’t human. They’re squishy beasties of various shapes and forms, and they’re up to no good.

John is the last guy anybody would think would “help bring about the end of the world.” He calls Dave to his aid, then while they’re at a diner, an alternative John calls to warn Dave about the John he’s having coffee and “The Sauce” with.

Straight-laced Dave struggles to figure out what’s happening. John struggles to stay straight long enough to pass on his warning to the world.

The only other person hip to what John seems to have found out is this mysterious TV mentalist (Clancy Brown, wacky and cast against type). If only they can get in touch with him.

People dissolve into heaps of snakes. The entire contents of a freezer, packets of pork, sausage and beef off the hoof, rise up and form into a menacing beast. The effects tip this off as an attempt to make a David Cronenberg (“Scanners,” “Naked Lunch”) comedy, with a few “Fright Night” touches.

The only effort to explain it all is having characters say, “Things are in motion,” and “There’s no time to explain all this.”

The supporting cast — Giamatti, Brown and Glynn Turman as a curious cop — gives us characters worth chewing on. But the leads simply aren’t wacky enough to make “Bill & Ted’s Cronenberg Adventure” come off. The middle acts bog down as writer/director Don Coscarelli tosses in animation and a dose of “Eyes Wide Shut”-masked nudity to maintain that trippy tone.

Confusing. Perhaps “John Dies at the End” is best appreciated while on “The Sauce.”

(At the Screenland Crossroads.)