Thirteen-year-old Clay, a boy who no longer believes in magic, tags graffiti on his classroom wall and, as punishment, is sent to a camp for wayward kids located on a volcanic island, where eccentric campmates abound, a ghost walks among the abandoned ruins of a mansion, and a dangerous force threatens to erupt with bad magic.

Cass and Max-Ernest discover the Museum of Magic, unscramble more coded messages, and solve new mysteries in their attempt to thwart the Terces Society's ambitions of discovering immortality.