The veteran detective Seo Do-cheol and his team at Major Crimes, relentless in their pursuit of criminals, join forces with rookie cop Park Sun-woo to track down a serial killer…

At work, she’s a renowned assassin. At home, she’s a single mom to a teenage daughter. Killing? That’s easy. It’s parenting that’s the hard part.

In the ultimate test of marriage, an agent-turned-househusband gets tangled in a perilous mission with his detective wife, who’s clueless about his past.