Stefan Marold was beaten to death in the prison shower, while awaiting trial for a millions fraud case at his employer's expense. All convicts refuse to talk, even Werner Gieß, Marold's only protector inside, obviously intimidated. Marold originally set up the secret accounts to finance his boss Christian Schmeil's many bribes, but started siphoning a large share abroad, while blackmailing Schmeil. All other detectives being known in jail, captain Kaiser must go undercover as 'transferred convict' and befriends Werner Gieß, the only match for prison bully gang leader Andreas Belzig, whom a star lawyer was promised, by Schmeil, to silence Marold. After Marold's corpse is stolen from the forensic morgue, whizkid Rico cracks Marold's musical accounting code, which later matches with the tattoo on his arm as key for the parallel accounting, which yields another suspect accomplice: Marold's lover Cornelia Mehring.