Detectives Helene and Thomas are quickly thrust into their undercover roles as a married couple. The pair get acquainted with the town's most prominent personalities and begin to stitch together clues.

The investigation has fallen off track, and Thomas is back in Germany. Helene has bigger things to worry about. A criminal she put behind bars has been released and is out for blood — Helene's blood.

The detectives' leads are drying up. The pair moves their investigation from land to the depths of the sea to investigate a shipwreck from 60 years ago.