A big amusement park is visiting Aidensfield for the annual fair. Greengrass buys a couple of paintings from two men working at the fair ground and tries to sell them to Alex Ferrenby who believes them to be worth a lot more than the £20 Greengrass is asking for them. He is right! 5-year old Brian Currie who is camping out with his parents at Mrs. Plummer's camp site goes missing. Claire Mercer, a patient of Kate's, suspects her son Michael has something to do with it.