Daisy and Hazel are finally back at Deepdean, and the school is preparing for a most exciting fiftieth anniversary celebration. Plans for a weekend of festivities are in full swing. But in the detectives’ long absence, Deepdean has changed. Daisy has lost her popularity crown to a fascinating new girl, and many of the Detective Society’s old allies are now their sworn enemies.

Then the girls witness a shocking incident in the woods close by—a crime that they’re sure is linked to the anniversary. As parents and alumni descend upon Deepdean, decades-old grudges, rivalries, and secrets begin to surface, and soon Deepdean’s future is at stake. Can the girls solve the case and save their home?