Kai Norden visits his dementing mother Martha in the rest home, far from enthusiastic about her suddenly revived old dream to visit Canada, which would require him accompanying her overseas. Several residents are pressing staff to investigate the disappearance of various a-items and some cash from their rooms. Asked as a cop, he calls in the team to look fro a thief. Suspects include the residents, among which only Martha isn't ruled out, and staff, from whom only last-recruited nurse Matthias Rehmert is suspended as easy scapegoat. Kai keeps searching and picks up accidental clues from his mother, whom Dr. Jasmin Jonas assures can still make her dream voyage if accompanied.

The precinct is eager to meet the new cop, succeeding Kai, who emigrated to Canada. Melanie hoped for a veteran partner but gets handsome academy graduated rookie Mattes Seeler, to work in. He proves a natural during their first case. Alexa Marschewski was mugged and raped on plane day. Prime suspect Fischer seems to have a perfect alibi and slips away from ER under Mattes' eyes, but the rookie guesses what unusual accomplice enabled that and works on him subtly.

Pro photographer Lasse Marquardt, who shot Melanie as poster girl for a police recruitment campaign, is badly beaten into hospital in an apparent robbery. Pre-teen son Max, due for a custody turn in Hamburg, was turned against him by his divorced mother, citing backlog financial support. Lasse was bothered by a disgruntled firm client and go tin financial trouble due to clients failing to pay. He also was shifty during Melanie's shoot, maybe weary of a loan shark. As his studio was ransacked, the team speculates he may have stumbled upon and shot something compromising, now missing, found with unfaithful celebrity Mark Wenske, who was blackmailed.

While Mattes attends, for security, the funeral of biker gang leader Olli Kenner, several of the mourners collapse and are hospitalized, apparently poisoned, while the urn disappears, no fingerprints. The team first looks into rivalry with the stronger Mambas gang. However, the well-planned urn theft only fits an internal motive, so they look into biker conflicts, and next Olli's cheated wife and conservative mother, stumbling upon Olli's anti-macho secret.

Law professor Jens Liebermann is taken to ER, no serious diagnose, after collapsing on campus during his jogging in front of a hanged effigy of himself. He claims it's a mere, yet unacceptable prank and hints at three wayward students, Lars Hansen (kin of detective Melanie), fanatical prankster Erik Bruckner and the latter's girlfriend and roommate Pia Rafalczyk, who spread the unsubstantiated rumor that Liebermann blackmailed her for sex. Team Mattes also looks into the strange reactions of the equally uncooperative professor's ambitious teaching assistant Cruschmann.

Med student Lisa (21), daughter of suspiciously clueless pharmacist Regina Krossmann, nearly died in a car crash, but her blood contains both a pharmaceutical cocktail and an incompatible sleeping pill. The latter is still unauthorized, so stolen from a promising research project. She also posed as a journalist student to interview missionary nun Agnes, who is visiting Hamburg from a Mexico, and has an old picture of her as juvenile, originating from Cologne like Regina.

Fear for Emma.

Family father Achim Kessler is hospitalized, badly stabbed in the gut, reporting he tried to break up two teens attacking a younger boy. The knave suspects Jens Schulz and Hakan Bulut are arrested, but convincingly confess only to minor, non-violent crimes, and no kid victim is found. Achim's firstborn Roman found them first, attacked with a baseball bat and was overpowered, bruised before Peter Leitl arrived to rescue him. Gently questioning kid son Jakob reveals Achim beats the boys' mother, who confesses as soon as Achim admits there was no threatened boy, the team suspects she's covering too. Meanwhile Wolle looses a parrot he was minding and the precinct prepares a surprise goodbye gift as it's Leitl's last day there.

Police chief Martin Berger opposes brat daughter Lena (16) attending a party with her Turkish new boyfriend, 'insurance apprentice' Kumsal, whose picture on a police record Martin assumes to prove he's a professional lover-boy, but the identification is disputable and the girl sticks to him. While Henning discovers an unlicensed brothel, a scattering juvenile harlot Nadine falls badly. House owner Henning claims it's run by an elusive Turkish tenant Tarik Alpay, whose mob may employ the lover-boy.