Horror genres tend to get sillier over time as we get more comfortable with our fears. Frankenstein eventually meets Abbot and Costello. Night of the Living Dead shambles inexorably to Dead Alive and Shawn of the Dead. With Rigor Mortis, Juno Mak tries to put that engine in reverse, attempting to breathe grim life into the geung si (Chinese hopping vampire) genre, traditionally spooky slapstick.
The resulting creep show has some frantic action scenes, but never quite enough spring in its step. A despondent actor -- Chin Siu-ho, playing a version of himself -- moves into a relentlessly gray Hong Kong apartment building to end it all. (The bleak setting emphasizes Ho's mood, but also presumably makes it easier on the CGI team, which does much of the film's heavy lifting.) After his suicide attempt is foiled, Ho meets the building's other denizens, a collection of supernatural tropes fallen on hard times.
Among the ex-vampire hunters, Taoist exorcists, and ghostly twins, the character who makes the greatest impression is Aunt Mui, an elderly widow attempting to resurrect her freshly deceased husband. Nina Paw invests Mui with grief and regret, whereas most of the others seem content to go through the roundhouse-kick, wire-fu motions.