Olivia's Secret Wish

When Olivia visits a pet shop for her ninth birthday she is presented with Jeremy, a plump brown gerbil in a glass cage. The shopkeeper knows it is not exactly the pet she was secretly longing for, but first Olivia must show him how responsible she can be. All goes well until the day she arrives home from school to find the cage left open, a trail of muddy footprints crossing the table top and Jeremy nowhere to be seen. After this, how is poor Olivia ever going to see her secret wish come true?
Suggested age range: 8 and upwards. With illustrations.