Time Out says
A good cop requires intuition, or so you learn when you watch cop movies. Facts get you only so far. But does intuition also include zipping yourself into a roomy valise, getting flung down several flights of stairs and channeling the inner thoughts of the deceased victim?
Maybe so: Inspector Bun (Lau) emerges from the tumble, offering, “It was the ice-cream vendor.” Of course he’s right; Mad Detective yokes forensics to the supernatural with a thrillingly silly sense of solemnity. Our hero sports crazy Einstein hair, no socks and a martyr complex
after being fired from the force, but when he’s contacted by a younger hotshot (On) to help solve an embarrassing internal-affairs case, you lean in, helplessly.
The poets behind such ridiculousness are codirectors Johnnie To and Wai Ka-fai, the former a Hong Kong action god, the latter a scripter of odd, inspired ideas. (An earlier collaboration followed a male monk turned stripper.) Every moment in Mad Detective seems engineered for maximum oddity; it almost becomes overwhelming as the multiple personalities that Bun can see become visible to us as well. Yet the movie feels adventuresome, too, a new bridge to Asia’s soulful ghost canon. It’s a metaphysical mystery masquerading as a doodle.
Cast and crew