Twelve-year-old Izzy Cervantes and her best friend Mackenzie have to spend their summer at Camp Foxtail... andthey're in different cabins! Izzy finds herself in the Willows cabin where her cabinmates have been friends forever - Izzy struggles to fit in. Then Izzy hears a prank war between Willow Lodge and boys' cabin Wolverine Lodge. It's her chance so she invents an older brother Tomas, a highly respected prankster. The effect is instantaneous; she goes from anonymous new girl to secret weapon. Izzy confides in her best friend and they spend the few comfortable hours they have together hatching perfect pranks for "Tomas" to suggest. The first prank goes off with a bang but soon Izzy becomes so focused on pranking that she starts neglecting Mackenzie-and even forgets her birthday. Mackenzie finally snaps and lets it slip to the entire camp that there is no Tomas!

When several campers at Camp Dakota report missing items and begin pointing fingers at a fellow-camper, a group of children search for the culprit. Includes glossary and experiments.