Stuck in a leaky beach house by the Australian seaside, all Anna wants is a holiday – but in the shadowy ghost town of Mermaid's Purse, something strange is going on. A famous explorer has gone missing, leaving behind their research about a long-lost shipwreck: a wreck that may be hiding a dark secret.

In the midst of a violent gale, Anna sets out to explore the town, sure that Max and the Professor will be safe indoors. But with a weird voice calling out to her from across the sea, and a network of cobwebbed tunnels running beneath her feet, Anna is about to learn that this ghost town might not be as empty as it seems ...