- You may be looking for Prisoner of the Sun.
The Doctor finds himself in London, having made an unexpected trip through the Time Vortex, but he doesn't know when. It's hotter than he can ever remember it. As he soaks his feet in the river, he is captured by a group of men, many of whom are former UNIT members, including Sergeant Benton. He is brought before Mike Yates, who is angry that the Doctor doesn't recognise him. He blames the Doctor for the current state of things. The Doctor notices a Time Lord message pod in Yates' office, unnoticed by the humans as it is a chronon out of sync with normal time. He also notices that Yates has an advanced interfacing device implanted in his nostril.
The Doctor is thrown into a cell. While imprisoned, he learns that a scientific elite known as Power Elite is in charge, and the former UNIT members who have captured him oppose Power Elite.
Elsewhere, Director Helios of SunTrap makes an address that is interrupted by terrorism. Helios escapes, but is actually part of the terrorism. He escapes, pleased that his plan is under way.
The UNIT group's headquarters are attacked, drawn to the site by the implant in Yates' nostril. A robot comes to attack the Doctor, but he disables it and takes its armour, escaping from his cell. On the way to Yates' office, he notes that Benton has been killed. In the office, he brings the message pod into the current time but realises it is not meant for him, but rather for Liz Shaw. Yates appears, under Power Elite's control, and brings the Doctor to his leader, Liz. When they meet, Liz tells the Doctor that she used the knowledge she learned from him to form the Power Elite, and when he protested, she had him placed in cryogenic suspension and used his brain linked to the TARDIS to continue using his knowledge. She shows him a disk of herself explaining everything that she learned.
When the message pod fails to open for Liz, he asks her to bring him to Director Helios. Helios reveals himself as a Solarian, whose species was wiped out by the Time Lords. He plans to use the humans as an army to destroy the Time Lords.
The Doctor throws a potato at Helios, which absorbs the microwaves holding Helios together. He is destroyed.
Liz informs the Doctor that she can rebuild again, but he has other plans. He sends a mental message to the Time Lords, who send him back to the time when Liz had just resigned from UNIT. He gives the message pod to this Liz, and when she opens it, it contains the disk that the other Liz had shown the Doctor. Liz realises she should not let that timeline begin, but can't unlearn what she has learnt form the Doctor. He tells her that she can choose not to use it.
On Gallifrey, two Time Lords discuss the Doctor's success in defeating Helios. They need to keep him busy on Earth, so one Time Lord says that the prison Shada has allowed the Master to escape. The other Time Lord leaves to warn the Doctor.
- Third Doctor
- Liz Shaw
- Sergeant Benton
- Mike Yates
- Director Helios
- Engineer Silo
- Sebastian Edge
- General Munro
- The Doctor encounters a Solarian, whose race were wiped out when the Time Lords created the Eye of Harmony.
United Nations Intelligence Taskforce
- The stories in Decalog are linked by the story Playback, in which psychic Silverman examines various items in the stranger's pockets. For this story, he examines the disk from a message pod.
- The prison planet Shada is known to the Time Lords. This seems to contradict the novelisation and the webcast versions of the story, which clearly illustrate the prison planet to be both lost and forgotten; as per the actions of Chronotis.
- The Doctor recalls his visits to Venus during his first incarnation. (COMIC: Doctor Who and the Rocks from Venus, PROSE: Venusian Lullaby)
- Edge remembers that Munro did "something important" during the Auton invasion. (TV: Spearhead from Space)
- Telecom Tower used to be known as the Post Office Tower. (TV: The War Machines)