The Doctor has been behaving suspiciously lately, and the Brigadier has been having him followed. He asks Liz to find out what's going on.
Liz talks to the Doctor, and he is close to telling her what he's been doing, but the Brigadier walks in, interrupting them. The Doctor leaves, and Liz angrily tells the Brigadier what he's interrupted, but he tells her they're going to Milton Bradbury.
The Doctor drives to Milton Bradbury, only to find it cordoned off. The Brigadier and Liz arrive, and the Doctor confronts the Brigadier. After some angry words, the Doctor leaves, accompanied by Liz.
The Doctor tells Liz that he had detected some signals indicating an alien presence. He has discovered that an alien crashed here in Milton Bradbury, and he wants to find it before anyone else does because it could be dangerous. The alien is an Eriscent.
As the Doctor and Liz walk through Milton Bradbury, looking for signs of the alien, they are confronted by the Brigadier, who tells them of a local death. The Doctor angrily storms off, followed by Liz.
Reverend Maurice Burridge has found the injured alien and has been keeping it in his spare room. Now, it leaves the room, trying to find someone with whom to communicate.
Val Jolley comes to the church to do the flowers. The alien finds her and tries to communicate with her. Terrified, she runs from the church to the nearest pub and collapses, dying.
The Doctor sees the church and deduces that the alien may be there. They introduce themselves to Reverend Burridge. The Doctor draws a picture of the alien on a pamphlet, and Reverend Burridge admits to finding the alien and keeping it here. He also dragged its spacecraft to the church and hid it. The Doctor warns Burridge not to communicate with the alien, whose method of communication is inventive but fatal to other life forms.
Meanwhile, the Brigadier is searching the church. He discovers the room where the alien was kept and discovers it is missing. He confronts the Doctor, Liz and Burridge. The Brigadier receives a communication that the alien is in the woods.
As the Doctor, Liz and the Brigadier head for the woods, Sergeant Mitchell, having seen the alien, dies.
Heading back towards the church, the Doctor offers the Brigadier a deal: he wants the alien safely captured and cared for until he can help it get off Earth. Just then, Burridge yells from the church window that the alien is here. It is climbing the church wall, heading for an open window. As the alien turns to face the UNIT officers below, the Doctor tells the Brigadier to order his men to stay put. A soldier aims his rifle at the alien, but Liz yells at him to stop and the rifle is taken from him. The alien falls, dead.
The Doctor has taken the rifle and shot at the alien to prevent its unintentional harming of any more men. Its fear at the sound of the shot caused it to fall.
- Third Doctor
- Liz Shaw
- Alistair Gordon Lethbridge-Stewart
- Sergeant Purvis
- Reverend Maurice Burridge
- Sergeant Mitchell
- Val Jolley
- The Eriscent
- The Doctor and Liz drive to Milton Bradbury in Bessie.
- 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 pamphlet with the drawing of the Eriscent.
- The Brigadier recalls his first encounter with the Doctor, then in his second incarnation, in the London Underground. (TV: The Web of Fear)