Synesthesia (2005)

Shin is a professional voyeur who provides live camera feeds of everything from the street corner to the public toilet. He is also afflicted freakish phenomenon known as synesthesia - a glitch in his wiring puts his five senses in a blender and spits out something close to insanity. A high-profile murder propels him into a psychological odyssey in pursuit of Picasso - a serial killer, snuff peddler and fellow synesthete - who leaves deadly hidden messages in his victims' blood that only Shin can decipher. Lulling his victims into a trance with a spellbinding video game, Picasso leads Shin down a mysterious, hypnotic trail of death.