Sieben Monde (1998)

Thomas Krömer follows the traces of a brutal murder in werewolf-manner out of personal interest. After investigating for some time, the traces all point to one person: himself. Now, he has to find out whether he surprisingly turns into a blood-seeking werewolf at full moon without knowing it or if there is an other solution to the murders. Police are getting pretty suspicious after Thomas' own grandmother has been brutally slaughtered in her little fairy-tale-fashioned house in the woods, and it will soon be time for a full moon...