In 2010, the North Yorkshire village of Melsonby was left in shock when postmistress Diana Garbutt was found murdered in the post office she ran with her husband Robin. He claimed she'd been the victim of a violent intruder, but as detectives probed further, suspicion began to fall on him and he was convicted of her murder and sentenced to life in prison in 2011. This documentary re-examines the case, featuring interviews with those convinced Robin was wrongfully convicted and others who are unsure and still suspect he is guilty.

Robin is sentenced to 20 years, but key evidence is missing, with none of his DNA on the murder weapon and data from the Horizon system unable be trusted.