Heroic Duo (2003)

Tough cop Ken Li (Cheng) is at the top of his game, but he's going to need some help to solve a grisly crime that the offender, a respected police officer, doesn't even remember committing. He seeks out Jack Lai (Lai), a former psychologist now in disgrace and behind bars, who has an uncanny ability to bend people to his will. Making an uneasy truce, this unconventional pair set out on a mission to find the man responsible, a master of hypnotism who will stop at nothing to get his revenge.