In the "Opel Zoo" near Frankfurt, a human hand has been found in the elephants' pen. As Inspector Oliver von Bodenstein and his partner Pia Kirchhoff rush to the scene, further body parts are found. Finally, on a nearby meadow, the rest of the body turns up: it belongs to Hans-Ulrich Pauly, a secondary school teacher and manager of a vegetarian bistro. Dr. Sander, the director of the Opel Zoo, tells the inspectors that Pauly was not particularly well-liked since he was passionately committed to protecting animals and nature – which led to some dust-ups with the Zoo officials. In fact, Bodenstein and Kirchhoff can't find anybody who really liked Pauly other than a few computer nerds interested in a mysterious internet business Pauly was operating. Beside Dr. Sander, other suspects include Pauly's ex-wife, who wanted to sell the property that belonged to both of them; the former student Patrick, who accused Pauly of having failed him deliberately; and Pauly's one-time school pal Stefan, who was being blackmailed by Pauly for an explosive incident that had occurred long ago. Just about everyone is glad to see Pauly dead – but only one person presumably killed him, and he or she has got to be found … especially since another murder has just occurred.