The riddle of the symbol takes Karp and Nurmi to investigate the overdose death of a young girl a year ago. Henna is exposed and enters the spring from the ditch. Nurmi gets hold of a video of a dashboard camera shot in Germany that shows a surprise related to Karp's man overrun.

Carp gets new information about her husband's past. The murder investigation takes in the footsteps of Karp and Nurmi's hard-hit family. At the same time, the mystery surrounding the pharmaceutical company is beginning to unfold. Carp realizes that Nurmi is also on the target of the killer.