Gardening and solving crime aren't what straight-A student Yeon Han thought she would be focusing on at her new school. But when she discovers a notebook that contains clues to a 15-year-old murder mystery, she and the other members of her new gardening club realize the murderer not only has access to the school—they probably work for the school. Can the gardening club squad figure out who committed the murder even though the principal and their teachers seem desperate to cover it up?