The door to Ms. Balian's darkened room clicked. From her hiding place, Nicki drew in her breath suddenly. Someone had slipped into the room! A dark figure moved quietly through the rows of desks and stood in front of the dresses, waiting . . .

Strange things are happening at Pine Grove Middle School-vandalism, dog-napping, stolen papers, and threatening notes. Is there a connection between the unusual girl and the mysterious mark that keeps appearing whenever something goes wrong? Nicki Holland and her best friends want to find out before something terrible happens to one of them!