Leslie is holidaying with her family near the sea. It should be an idyllic time, but she is furiously unhappy with Gilly, her new boss-queen stepmother and is exasperated by her father.
Exploring rocks near their holiday cottage, Leslie discovers a fearsome secret place. Despite meeting a fabulous boyfriend, she becomes obsessed with what is concealed there. When Gilly forbids Leslie to see her boyfriend, revenge and obsession lead to horrific danger. It takes a dramatic night-time cliff climb and rescue for stepmother and stepdaughter to be reconciled.