Starring Daniel Wu and Nick Cheung. In Cantonese, with English subtitles. Rated 14A.

It’s clear why this Hong Kong import, a vivid thriller about a cop with issues, was not called The Well-Adjusted Happy Person Within. Dave (Chinese-American model turned actor Daniel Wu, his natural handsomeness suppressed by an institutional haircut) is modest, diligent, and driven, but a certain lack of social skill has kept him, at 35, a patrolman.

The movie revolves around a chance meeting between Dave, currently stationed in a hospital, and a trauma victim for whom he provides a life-saving transfusion. The recipient turns out to be Hon (Nick Cheung), a notorious gunrunner who has just murdered a pair of cops.

This act of dutiful heroism merely gives Dave additional stress and grief at work, as he is berated by his fellow officers for saving a cop killer. Meanwhile, Hon himself is struggling with his clientele, in particular a band of trigger-happy jewel thieves who wear old-timey demon masks for reasons of disguise and director Dante Lam’s preoccupation with stylization.

A John Woo movie might dwell on the romantic notion that men of blood (in this case, literally sharing it) are more alike than not. That Demon Within does acknowledge this idea; the bones of a workplace comedy are seen as Hon and Dave attempt to overcome incompetent coworkers.

But That Demon Within is not a buddy-cop movie. It is a work of psychological horror with arguably too much psychology (a sympathetic supervisor forces Dave into therapy, obliging numerous flashbacks), in that the character’s descent toward the title would have happened with or without his tragic good deed. But the trip itself is exciting and curiously beautiful, shot with a restricted palette and camera flourishes galore—a perfume commercial in hell.