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!

Christine's friends help her investigate the cause of her older brother's increasingly violent behavior after witnessing his frightening outbursts.

In the gathering darkness, Nicki and Christine swam quietly toward the Mary Celeste II . The water was as black as ink around them, and Nicki tried not to think of the living things that might be passing by her in the warm water. They reached the stern of the boat where the overhead light on deck threw shadows in the water. Nicki lifted her face mask. "Are you going to climb up, or should I?" Christine's mouth fell open and her eyes bugged. "Behind you," she squealed. "Look!"Nicki whirled around. Behind her something was rising out of the water-something big and dark and sinister, with arms like a giant sea serpent! Nicki Holland expected fun and sun in the summer before her eighth grade year-not mysterious strangers and counterfeit cash! Nicki, Meredith, Kim, Christine, and Laura are warned to leave the mystery alone. But when Nicki is threatened, she has to solve the mystery to save her own life!

Nicki and her friends try to find out who is behind the mysterious occurrences at the small local bowling alley.

Nicki and her friends spend their flight home from Ireland trying to figure out who is the mother of the baby left in their care and unknowingly convincing a young Irish woman not to have an abortion.