A low-ranking cop often relegated to desk duty, middle-aged Tsim Kin Yip (Simon Yam) lives a stable, mundane life with his young yoga instructor wife Ann (Annie Liu). The monotony is broken one day when he interrogates Kwan Ping Man (Nick Cheung), a nervous, profanity-spouting man caught spying in the women's bathroom. Kwan, who seems to have more than a few screws loose, confides to Tsim a shocking secret: a ring of women conspiring to murder men. Everyday, plans are whispered in restrooms and deaths are carefully engineered, so that men die unnoticeably from "accidents" that are anything but. Tsim initially dismisses Kwan's conspiracy theory, but then clues crop up suggesting there is something fishy at work. Both his marriage and life could be at stake as Tsim becomes increasingly obsessed with cracking the case.