Homeless Manfred 'Manni' Keller drowned, dumped in the Neckar after a fist fight. He recently rowed with his ex Conni Peterson. Fellow dwellers being uncooperative with cops, Jo goes undercover as if homeless. Jo is taken in the care of Klaus Toner, Manfred's buddy, who later offers the studly newcomer a lucrative gig: illegal knuckle box fights. Rico finds a trial to wealthy, cocky student Elmar Frei, who makes 'donations', in fact payment for fights. Jo also befriends Thommi Kutz.
—KGF Vissers