Not since the glory days of John Woo’s pre-Hollywood peak have I had so much fun watching an action movie as with The Viral Factor, a Hong Kong production so overstuffed with melodramatic plotting and pyrotechnics that I watched most of it in a fit of happy giggling. Had I been watching it in a theater instead of on a screening DVD, I would probably have been asked to leave.

Taking the opposite tack of American movie stories, this screenplay starts from the public and moves into the personal. A scientist has developed a new strain of smallpox that is resistant to the vaccines that eradicated it from the world by 1980. Terrorists acquire it and launch a plot to re-introduce it to the world, after which they will make a fortune selling the vaccine they have prepared.

Plenty of plot there for a thriller. But after setting that up, the film seems to change directions ever five or 10 minutes. We follow a tangent about Jon (Taiwanese superstar Jay Chou), agent for the International Defense Commission, who took a bullet in the head in the attack that lost the virus and killed his fiancee. In two weeks the unremovable bullet will cause his complete paralysis. Then there’s Yeung (Nicholas Tse), a criminal in Malaysia who escapes after being sentenced to 10 years in prison. He is hired by a corrupt cop to kidnap a research scientist from the Asian Center for Disease Control.

Disease? Hey, wasn’t there something about disease back at the beginning of the movie?

One of the most expensive Asian films ever made (though it’s estimated $17-25 million budget is about 10 percent of Disney’s John Carter), The Viral Factor is preposterous, but never tips over the edge to the point where you want to laugh at it. It’s a fully fleshed product of a cinema where realism is appreciated, but only to a certain point. The nonstop action relies on the old-fashioned kind of effects—exploding cars careening down cliffs, flaming stuntmen flying through the air, helicopters careening around skyscrapers, that kind of thing. When a character outlives his usefulness to the plot, he’s likely to be hit by a bus—literally. Good guys confront their dark sides, criminals probe their souls, and bullets fly like snowflakes in the winter of 1977. I couldn’t have enjoyed it more.

Watch the trailer for The Viral Factor