What would you do if your adult children developed an age-defying disease that made them regress to childhood in front of your eyes? How would you cope with seeing them go from man to boy and looking after them 24 hours a day?

This documentary tells the harrowing but brutally honest story of Tony and Christine Clark and their two sons Matthew, who's 39 and Michael, who's 42, as they live and cope with this dreadful condition; not once, but twice.

Michael and Matthew Clark from Hull had lived normal lives until their late thirties. They were totally unaware their brains were carrying a deadly neurological time bomb: a rare and little known condition called Leukodystrophy.

The condition causes a progressive loss of every neurological function - speech, memory, movement, sight, hearing, touch, eating, swallowing - and normally affects children.

To discover a late onset strain is exceptional and what makes it even more astonishing to the Clark family is that it should attack two members of the same family.

Christine and Tony thought their parenting days were over. They had taken early retirement and were enjoying a pleasant ex-pat life in Spain. When news of their sons' illness and rapid deterioration reached them, they had to abandon their life abroad and return to the UK.

The family moved into a cramped one-bedroom flat and the parents were forced to look after and care for their two 'boys' 24 hours a day.

This film follows the Clark family on their fascinating and traumatic journey as they struggle with their day-to-day life, trying to come to terms with watching their grown-up sons become young boys trapped in adult bodies.