Erhard Lechner was fatally stabbed in his smartphone repair shop. Sven Hansen and recent detective Kilian Kaya first suspect Lechner's junior partner Adrian Ramp, his cahoot in fraudulently using cheap non-original components. Lechner had an affair with employee Christiane Häberlein, who recently quit, reason unclear, and now works for Jo, as Sven, who knows her name keeps popping up in cases, only finds out later by accident, while she drives Joe to despair being incompetent and repeatedly summoned for questioning. Did fresh widow Fanny Lechner find out and kill him? Businessman and last known client Ludwig Bukowski reports a woman leaving the shop, unidentified. Jo needs help to cater from "Times Square" in the music academy, can't count on Christiane, so Lange volunteers.