One is a 15-year-old boy, Samuel Miles, a.k.a. 'Smiler', wrongly convicted of theft and sent to a young offenders institution. The other is a cheetah, Yarra, a restless resident of Longleat Wildlife Park. Both are in danger from the outside world - and each other - but somehow their lives become inextricably bound up as they fight for survival on the edge of Salisbury Plain.