Arne Dahl's A Unit has been disbanded for the last two years but when a wave of brutal murders hits Sweden the National Police seize the opportunity to reinstate the unit under the lead of Kerstin Holm (Malin Arvidsson). Kerstin builds her team with former members of the unit Nyberg, Chavez, Svenhagen and Soderstedt, but she is also assigned a new recruit, the somewhat reluctant Ida Jankowicz, a wiry, yet powerful, rookie with exceptional language skills. Paul Hjelm (Shanti Roney), previously a key figure in the A Unit, has been promoted to a job as head of Internal Affairs. At first, he and the A Unit are pretty far removed from each other, but their paths will cross sooner than any of them could imagine. Demands and expectations k have never been higher and a cold wind blows through the corridors at the National Police headquarters.