When an anonymous note threatens someone they love, twins Sadie and Saskia Dopple are thrust into a series of crimes that look suspiciously like something from the pages of a mystery novel.

Erik Morrissey Ganger and his friend, Sadie Dopple, meet a wealthy recluse while trying to escape tunnels under Isambard Dunstan's School for Wayward children in order to pursue a former foe who has kidnapped Sadie's twin sister.

In 1935, while preparing to write a newspaper story about a theater production of Macbeth in her hometown of Cincinnati, twelve-year-old Kit discovers that a thief is stealing from the box office.

While at St. John National Park in the Virgin Islands for a seminar on coral reefs, the Landons help a wealthy thirteen-year-old to find his birth mother, who he believes is in danger.