Calculi Lupae

David had always liked Sheri, but was always too nervous to say or do anything. Now, though, he was finally going out with her, which would be great if she didn't act so uncomfortable about his necklace... The necklace had been a gift from his grandmother before she died, but lately it seemed like it was acting... odd. Strange things were happening, and David was sure that the necklace had something to do with them. But why was a strange and powerful monster, who seemed intent on killing both him and Sheri, so interested in it? What was the meaning of his grandmother's strange poem? And why did Sheri seem to know more than she claimed?