Billy Bailes is a runaway who makes a hideout in a garden shed. Nicola and Jackie bring him food and keep his secret. Scared and lonely, Billy won't talk until his friends and his love of drawing birds, especially magpies, lead him to find a home with them as looked-after children. It's looking good for Billy until a holiday game of spies throws them into a search for buried treasure and they come face to face with the shady antiques thieves who want Thomas a Becket's jewelled cross for themselves.
