More in the shaggy-dog style of his Running on Karma or Fulltime Killer than the epic scope of the Election movies or Exiled, this straight-faced send-up of the mad-genius-cop genre by Johnnie To (directed with Fulltime Killer author Wai Ka-Fai) is as divertingly daft as its hero: a schizoid ex-detective (Lau Ching Wan) with intuitive powers that can only be described as uncanny. (After ordering a rookie to hurl him down several flights of stairs in a suitcase, he emerges bloodied but thunderstruck: “The ice-cream man is the killer!”) Five years after he’s booted from the force, along comes a case that calls for some crazy: a cop (Andy On) whose multiple personalities may have caused his partner’s disappearance and a string of lethal robberies. Apart from its inventive depiction of the weaknesses that tough guys try to hide, Mad Detective is a slight work from the wildly prolific To. But as the directors amuse themselves in devising new ways to visualize schizophrenic dementia—casting a half-dozen different actors as the suspect’s splintered psyche in a kind of psychotic entourage—the movie makes deadpan sport of its convolutions. Even if you lose track of who’s shooting whom and why during the abstract climactic face-off, the clever last shot shows you’re not alone.