At a top secret UNIT facility known only as "the Warehouse", Dr Sally Arnold has been studying a Nestene energy unit with no results. As a last resort, she subjects the artifact to cosmic signals from UNIT's most powerful deep space scanning satellite. This causes a violent energy release that kills her assistant, Janice. The energy unit has disappeared.
A containment team, led by a psychic UNIT operative named Lockwood, has been dispatched. Among Lockwood's abilities is the ability to access all information from any computer mainframe in the world with his mind.
They soon learn that the Nestene energy unity has taken on a mobile form, and that there is an Auton copy of senior archivist Graham Winslet. The real Winslet is still alive, his mind being used by the Autons as a resource of information. The energy unit then merges with the Auton Winslet.
Several dormant Autons in the Warehouse come back to life and the building becomes a battlefield. They are eventually defeated with the weapon created by the Doctor and Liz Shaw in Spearhead from Space. The Auton Winslet then liquefies and escapes through a ventilation shaft.
- Lockwood - Michael Wade
- Dr. Sally Arnold - Bryonie Pritchard
- Graham Winslet - George Telfer
- Dr. Daniel Matthews - Reece Shearsmith
- Sergeant Ramsay - Andrew Fettes
- Janice - Verona Chard
- UNIT Soldiers - Roy Hughes, Gabriel Mykaj, Mike Parry, David Ringwood, Richard Smith
- Autons - John Ainsworth, Gareth Baggs, Blaine Coughlan, David Ringwood