When two 13-year-old girls discover that Britain’s tiniest mammal — the harvest mouse — is vanishing from the wild, they launch an ambitious rescue mission. Breeding hundreds of mice in their bedrooms and garages and then releasing them into a new nature reserve near their homes in Devon, their efforts capture national attention and a visit from Britain’s leading wildlife campaigner, TV presenter Chris Packham. This heartwarming short documentary follows Eva and Emily's inspiring bid to bring back one of Britain's “missing species”.