Iain lives in the Highlands where a movie is being filmed. He has been chosen to play a part alongside twin child stars Carol and Melody. Odd and unpleasant things start to happen. Wild animals are released from a nearby open-air zoo – wolves and a wild ape disrupt filming and threaten the children. When they join up with old friends of Iain, Raj and Raveena, they witness one of the film crew being attacked and injured, and discover jewel thieves are operating in the area.

The Laird's mansion (jokingly called Movie Manor by the locals), where all the actors are based, is burgled and personal items stolen. The Laird blames friends of Iain for everything, so the children investigate – a rather awkward investigation as they need to squeeze it in between filming scenes in the movie. Could their burglar be the same burglars who are stealing jewels? Are they releasing the wild animals?

Despite facing terrible danger, the children solve a puzzling double mystery – and discover an unexpected secret about the manor.