Having solved the matter of the Radiant Boy, Riley, Buttercup, and Bodhi are enjoying a little time-off. But then Riley encounters a young ghost named Rebecca. Despite Rebecca’s sweet appearance, Riley soon learns she’s not at all what she seems. As the daughter of a former plantation owner, Rebecca is furious about being murdered during the slave revolt of 1733. Her uncontrollable anger is keeping other ghosts, who also died in the revolt, trapped in a shimmering bubble. And when Bodhi and Buttercup inadvertently fall into Rebecca's trap, Riley is the only one who can save them.