Lake Constance is considered Europe's largest ship graveyard. As a result, it attracts treasure hunters from all over the world. And that's exactly the kind of treasure hunter the WaPo spots on its patrol. Diver Arno Gierke admits that he misses both his partner and his boat.

The body of a young, athletic man is floating lifelessly in the lake. When Nele and Paul pull the surfer—who is already severely hypothermic—from the water, it's too late to save him. Daniel Dellbrück was the victim of deliberate blows—with a paddle?

What starts out as a routine procedure suddenly turns into a murder case. The animal spotted floating in Lake Constance turns out to be a corpse dressed in a fur costume and wearing a carved wooden mask. Achim Tilger, the deceased, had just suffered an unprecedented business collapse.