The heinous murders committed by a serial killer keep the residents of the small town of Sountheim in suspense. The "Vorstadtripper" special investigation unit and chief investigator Müller Karl Albertinari are faced with a mystery. In the middle of the investigation, SOKO investigator Torben Win makes a gruesome discovery. A far greater danger than the Suburban Ripper lurks for the residents of Sountheim: an invasion of flesh-eating backpacks that have come to life! Together with Inis and Jannette, Torben flees to an underground bunker system. Supposedly safe from the backpacks, clues are found in the corridors that suggest that the Suburban Ripper committed his murders right here. Now it's not just the bloodthirsty backpacks that are after them...