In a top-secret UNIT warehouse Dr Sally Arnold is studying a Nestene energy unit with little success. Until she subjects it to cosmic signals that activate it and it awakens several dormant Autons stored in the facility.

Auton 2: Sentinel was the second story in the Auton Trilogy of video dramas produced by BBV Productions in the late 90s, and a sequel to the first, Auton. Like most video dramas of this era, it featured characters and concepts from Doctor Who but did not include any main characters from the series. Two years after the incident at the UNIT warehouse a lorry transporting Autons from there to another UNIT facility is hijacked by it's cargo. Lockwood and another psychic, Natasha, trace the Autons to Sentinel Island.

Lockwood and Natasha have returned to the mainland from Sentinel Island but find that the population of the town of Millhampton have vanished. The pair discover that the nearby hospital is the Nestene base of operations.