The Devonshire monastery garden is deceptively serene on a summer day. Brother Adam is endeavoring to breed perfect bees as his parting gift to the world--placid workers and champion honey-makers.
The abbot sends young Joe to help the old beekeeper as penance for stealing apples from his orchard. The boy is bitter after losing his father and has more to contend with than a grouchy monk and stinging insects. When his older cousin, Emily, comes from London, she dreams of solving a mystery buried on the grounds by medieval monks. She inveigles him to join a hunt that ends at the bee-yard, but the village gang leader, Brad, is on the track. Only the bees know the secret.
Another drama is unfolding inside the hive unbeknownst to the keepers. When the monk transfers his prize queen, the "Peacemaker," to another hive, the resident bees revolt against her new brood. Tensions escalate after a nursing error produces the mutant "half-queen" Sundew. When her nemesis, Hemlock, fails to eliminate her, Sundew leads an insurrection against the rival brood. After the bee war, Hemlock seeks revenge and thus begins Sundew's perilous journey.
The boy and girl save the bee from a carnivorous plant, but Sundew faces more trials before reaching home to find the Peacemaker family has swarmed away. Hemlock's brood stays to defend the hive from attack by a monster they thought only existed in myths. The former enemies unite to drive it away and then Sundew goes in search of her queen.
The monk is desperate to recover his precious brood after the vandal wrecked the hive. Joe recognizes Sundew when she visits the monk's tea party and follows her beeline to recover the swarm. No longer a reluctant beekeeper, he has discovered a talent and as the bees' new guardian only he can resist the malice still threatening them.
Troubles that weigh on Joe's resilience are mirrored by the antagonism between broods of insects inside the hive. The peace of the bee-yard can't be restored by conquering adversaries but needs the waste of violence to be understood and forgiven.
The author pledges profits from royalties to charities for children with cancer.