Philip befriends Jack and Lucy-Anne at summer school and invites them home to Craggy Tops to meet his sister Dinah. A terrific friendship develops and one day the children head off to explore an old smugglers' tunnel and discover it leads all the way back home to Craggy Tops. When the children are later taken out on a boat trip they soon find themselves on the trail of money launderers in the disused copper mines on the island. (thetvdb.com)