Dublin, 1912, and the summer stretches out before twins Tim and Deirdre, and their friend Joe. Then Deirdre spots Joe at the beach – when he’s supposed to be 120 miles away in Limerick. When Joe swears that he really was away, they know they have a mystery on their hands.

Who was the boy at the beach? And can the friends track him down? Meanwhile orphan Billy Smith discovers that he has a double in the outside world. But if he’s to make contact with his lookalike he needs to get out of the orphanage. And escaping from the clutches of his enemy, the brutal Brother Walsh, won’t be easy.

For Deirdre, Tim, and Joe it seems like another adventure, and they excitedly make their plans. As they begin to uncover the facts, however, the shocking truth emerges – and their lives will never be the same again.