On the afternoon of Sunday 1 May 2016, 31-year-old mother of three Natalie Hemming vanishes, seemingly without a trace. Forty eight hours later, her frantic mother phones 999. 'What's the specific concern that's caused you to call the police?' asks the operator. Natalie's mother says: 'Him'. That phone call launches one of the biggest missing person searches ever seen at Thames Valley Police. This gripping programme follows the investigation hour by hour as the police have to decide if Natalie is alive or dead. With extraordinary access to the minute-by-minute police investigation and to Natalie's family and friends as they struggle to come to terms with the situation that's unfolding around them, Catching a Killer: The Search for Natalie Hemming follows the case from the extraordinary hours before the arrest to its heart-breaking conclusion.