The Swedish town of Linköping is bathed in Spring sunshine. The trees are blossoming and families are having breakfast at outdoor tables in the main square.

Then a deafening explosion rips through the air.

Broken glass and tulip petals cover the cobblestones, and two little girls, twin sisters, are killed while their mother is left fighting for her life.

Detective Inspector Malin Fors has just attended her own mother's funeral when she is summoned to the devastating scene. But, although Malin is plagued with questions about her past and the secrets her mother never revealed, she must once again bury her own pain if she is to find Tuva and Mira Vigerö's killer before he strikes again.