Med student Fabienne Lüders is found fatally stabbed in a hotel room booked by Robert Kaiser, the latest of series of men she seduced despite engagement or marriage, yet never had sex with nor was paid by, including blackmailed Tobias Kern. She as employed by Sybille Hummels' specialized detective agency, to test infidelity, 60% failing. Fabienne's doting housemate, biology student Lukas Amling, believed her Lesbian. Siren victim Kai Engelhard rented the car used to attempt running over Sybille Hummels. Meanwhile Dominik decides against a promising date in favor of his possibly unfaithful (ex?) lover.
—KGF Vissers