Paula de Jagger is a Dutch foreign exchange student staying with Nancy’s neighbors, the Moorelys. Paula is smart, pretty, and popular, but something is very wrong. Lately she’s been getting mysterious phone calls, sneaking out of the house in the middle of the night, and lying to cover her tracks.
Nancy wonders what dark secret the Dutch girl is trying to hide. The mystery turns sinister when fire hits the Moorely home — and the evidence points to arson! But is Paula the source of the trouble or a victim of it? Nancy must find the answer before danger strikes again.