A royal child in hiding. A traveling circus with secrets. And a sudden disappearance. When Bill vanishes during a cavert mission, the children are sent to a sleepy village for safety but something isn't right. The local circus is no ordinary spectacle. Whispers pass between acrobats, the clowns watch too closely, and Lucy-Ann meets a mysterious girl with a hidden past. Jack stumbles upon a torn message, Philip befriends a lion and a tightrope walker, and Dinah notices that the circus is packing up in the dead of night. With no time to spare, the children set out to follow the fleeing performers, desperate to uncover the truth. But when they finally leap aboard the last carriage of the moving train, the heavy door locks behind them, plunging them into darkness-and straight into danger.