The Seeds of Doom is the sixth and final serial of the 13th season of the British science fiction television series Doctor Who, which was first broadcast in six weekly parts on BBC1 from 31 January to 6 March 1976.
In the serial, the Fourth Doctor (Tom Baker) agrees to go on one final mission in his role as UNIT's scientific advisor to investigate a mysterious pod found in the Antarctic. However, the crazed millionaire and plant collector Harrison Chase (Tony Beckley) is also interested, and has sent his violent henchman Scorby (John Challis) and the botanist Arnold Keeler (Mark Jones) to acquire the malignant alien plant for his personal collection.
Plot
In Antarctica, British scientists Charles Winlett and Derek Moberley discover a pod buried in the permafrost and take it back to their camp. John Stevenson, the base botanist, identifies it as vegetable-based and estimates it has been buried in the ice for twenty thousand years.
In London, Richard Dunbar of the World Ecology Bureau shows the Fourth Doctor photographs of the pod at the urging of his superior, Sir Colin Thackeray. The Doctor believes it to be extraterrestrial. He tells Dunbar to tell the expedition not to touch it until he arrives.
Back at the base, Stevenson discovers that the pod is growing larger and he believes it is absorbing ultraviolet radiation. In England, Dunbar visits the estate of millionaire Harrison Chase, who considers it his mission to protect the plant life of Mother Earth. Dunbar gives Chase the location of the pod. Chase sends his men, Scorby and Keeler, to retrieve it.
At the base, the pod opens and stings Winlett. When Stevenson and Moberley find him, Winlett's face is covered with green hives. The Doctor and Sarah arrive and find that Winlett's face and body are rapidly becoming covered with green fungus. Outside the base, the Doctor uncovers another pod and notes that they travel in pairs. Winlett's blood is found to contain no blood platelets, but instead has schizophytes – microscopic organisms akin to plant bacteria. The Doctor tells Sarah that Winlett is turning into a Krynoid, a galactic weed that settles on planets and eats the animal life. Scorby and Keeler arrive, claiming that their private plane got lost.
Moberley is killed by Winlett. Transformed into a Krynoid, Winlett flees the base and shelters in the outside generator hut. Scorby and Keeler steal the remaining pod then escape in their plane. The Doctor and the others are attacked by the Krynoid, which kills Stevenson. The Doctor and Sarah flee as a bomb set by Scorby and Keeler destroys the area. The Doctor and Sarah are picked up by a team from South Bend, while Scorby and Keeler return to Chase in England with the second pod. Dunbar warns Chase that the Doctor and Sarah are still alive and are scheduled to meet with him and Sir Colin in two hours.
At the meeting, the Doctor and Sarah describe the theft of the pod. He tells Dunbar to arrange for him to go to the Botanic Institute. As they leave a driver meets them. However, the limousine stops in the countryside, and the driver orders them out at gunpoint. The Doctor jumps the driver and punches him out. The Doctor and Sarah search the car and find a painting by Amelia Ducat, a flower artist. When they visit her, Ducat tells them that the owner of the painting is Harrison Chase, who never paid her for it.
Chase orders Keeler to inject the pod with fixed nitrogen. When the Doctor and Sarah try to sneak into the mansion, they are captured and brought before Chase, who decides to show them around the mansion and his plant laboratory before he executes them. When Scorby escorts the Doctor and Sarah into the gardens to kill them, they overpower him. Sarah escapes but is captured again. The Doctor rescues her and in the confusion, a frond from the pod stings Keeler's arm. Keeler soon begins to transform.
When the Doctor returns to the laboratory, he is captured and taken to the compost room, where Scorby activates the crusher. Sarah escapes back to the house, attracts Ducat's attention and asks him to take a message to Sir Colin. Outside, Ducat enters a car with Sir Colin and Dunbar inside and tells them what Sarah said. Dunbar, realising he has made a terrible mistake, says he will get the Doctor. He tells Sir Colin that, if he does not return in half an hour, to return to London and call UNIT.
Sarah turns off the crusher in time to save the Doctor. Hargreaves finds that Keeler has almost completed his transformation and runs in a panic as the creature frees itself. In the mansion, Dunbar pleads with Chase to abandon the experiment as Hargreaves reports Keeler's transformation to Chase. Dunbar goes to get help and is pursued by Scorby.