Jessamy Harrison is eight years old. Sensitive, whimsical, possessed of a powerful imagination, she spends hours writing, reading or simply hiding in the dark warmth of the airing cupboard. As the half-and-half child of an English father and a Nigerian mother, Jess just can't shake off the feeling of being alone wherever she goes, and other kids are wary of her terrified fits of screaming. When she is taken to her mother's family compound in Nigeria, she encounters Titiola, a ragged little girl her own age. It seems that at last Jess has found someone who will understand her. TillyTilly knows secrets both big and small. But as she shows Jess just how easy it is to hurt those around her, Jess begins to realise that she doesn't know who TillyTilly is at all.