Zwietracht der Hyänen

Jo, Harri, Nik and Beppo meet on a field to dig up their hidden loot. Their buddy Lenz is missing - they end up digging without his help. At the bottom of the ditch, they discover Lenz's body instead of the loot they were after. Nobody knew of the hiding place except for them - hence, one of them is a murderer. But who?