It's rare for such an innocent hobby as birdwatching to end in death. The Washington Post found Sam Birkner, an unemployed amateur ornithologist, at an illegal dumping site on the shore of Lake Constance. The man had been observing not only birds but also people—such as Judge Marla Kohnen, who regularly dismissed Birkner's complaints on the grounds that they were trivial. But the judge was biased, as Nele discovers. She knows Ludwig Kienast, the target of most of Birkner's complaints. The troublemaker Birkner also harassed the renowned ornithologist Kati Hendricks. Sam Birkner accused her of errors in her doctoral dissertation and wanted to make that public. Finally, Jakob and Julia wonder why, of all people, the resolute Ms. Nökel claims to have had a good relationship with Birkner. The curious neighbor failed to notice, of all things, the break-in during which a computer was stolen. The case is becoming increasingly murky.

Nele and Paul barely manage to pull Helmut Pohl out of the water. He had attacked the sailor Lorenz Haller on his boat. Haller was able to fend off the attack. Pohl ends up in the water and falls so badly that he slips into a coma at the hospital. It soon turns out that the man who suffered the accident is the boat's real owner. Haller had bought it in good faith online—from a scammer. Julia and Jakob discover that the payment went to the account of 19-year-old Mila Simic. But Mila is also a victim. She had fallen in love with Jonas, who was just using her. His real name is Maximilian Hofer. He is known to the police as a violent repeat offender. Mila isn't willing to let the matter rest. She meets with Maximilian. A big mistake. Because Nele and her team are also on the trail of this unscrupulous guy.

Jakob sees Vanessa as the woman of his dreams. But Vanessa is recovered dead from Lake Constance—drowned. Paul wants to immediately remove his colleague from the case due to a conflict of interest. However, the worldly-wise Nele fears Jakob might go it alone and keeps him on the team. He immediately sets his sights on Vanessa's ex-boyfriend, Bastian. Bastian had followed her from Düsseldorf to settle debts from a business venture they'd shared. Bastian claims to have spent the night with the receptionist, Marianne Tillich. What about Yvonne, Vanessa's sister? She lives with her boyfriend Georg in a house by the lake that runs a boat rental business. She would have had to give up that idyllic life and sell the house to pay out Vanessa's share of the inheritance. Yvonne presents the investigators with yet another version of events. She says she wanted to sell the house and move to Spain with her sister—without Georg, but also without Jakob. This sends him into an existential crisis.