The new series following the life-saving work of the medics of a mobile intensive care service for children continues. The highly specialised emergency teams from the Children's Acute Transport Service, CATS, make sure critically ill children who need intensive care get it, wherever they are. The team is called to a baby who is so sick, her heart has already stopped once, she needs to get to a specialist intensive care unit urgently; a teenage boy who is in a diabetic coma; and a three-year-old little boy who is back in hospital for the 20th time. The team need to get him to Royal Brompton's children's specialists to investigate the cause of his continuing problems.