The police have been called to the scene of an attack on a man who has been left badly injured at home.
He is transferred to hospital to receive urgent specialist treatment for brain trauma that doctors believe is so severe he is unlikely to survive. Investigating officer Alicia Lawrence, of Bedfordshire Police, realises she already knows the victim because just a few days before she met him when he came into Luton Police Station.
At the time he seemed healthy and happy. As she pieces together what happened between him and his partner in the days after, she is haunted by a fear that more could have been done to protect him, she admits: 'I knew it would come to this'.
When the man dies of his injuries she is transferred to the Major Crime Unit to help investigate. Cameras follow every twist and turn of a deeply personal investigation where detectives try to find out what lay behind the attack, as they ask the question: What, if anything, could have saved his life?
24 Hours In Police Custody airs Monday at 9pm on Channel 4.