When Peter checks on his 82-year-old father at home one morning as normal, he finds the house empty. Suffering from advancing dementia, Archie has vanished - leaving no sign of where he might be. PC Geoff Moore's job is to get as much information as he can from Peter in the hopes of learning whether the problem is physical or whether somebody has taken advantage of his vulnerabilities. As an ex-paratrooper, Archie has been physically fit all his life and has been struggling to accept his increasing fragility. Dementia sufferers are known to travel vast distances when they disappear, and a full-scale land and air search is launched to find Archie. But as hours tick by without so much as a single confirmed sighting, and a neighbour comes forward with CCTV of potentially suspicious activity at Archie's home address, the police begin to suspect foul play.