The Lair of Zarbi Supremo was a fifteen-page prose story published by World Distributors in September 1965. It was the first short story to be published in the Doctor Who Annual 1966. The enemy of the story was the Zarbi Supremo.
The Doctor returns to Vortis. He hears a voice calling through his radio to warn Earth about the Zarbi Supremo. Using the directional aerial on his radio, the Doctor locates the source of the transmission. It is a metal sphere half buried between two Zarbi anthills. Once inside, he finds it is a spaceship, the Solar Queen. A tape recorder is producing the radio warning.
Investigating further, he finds a boy, Gordon Hamilton, and his unconscious father. Gordon tells the Doctor that the other six crew members went to explore nearby spaceships that were also on the planet's surface, ships that they believe the inhabitants of Vortis are planning to use for an invasion of Earth. The Doctor, confused because of Vortis' distance from the Earth, isn't sure of the boy's story, but Gordon tells the Doctor how his father, before falling unconscious, eavesdropped on the Zarbi's telepathic communications. Gordon's father understood that the Zarbi were after the Earth's water and vegetation and that the invasion was being planned by the Zarbi Supremo. The Doctor and Gordon search for the ship's missing crew members.
Outside the Doctor and Gordon come across motionless Zarbi. At first thinking they may be dead, the Doctor finds that these Zarbi are made of metal and seem to be robots. Opening the robot Zarbi, the Doctor finds a dead Menoptera, one of the peaceful, butterfly-like inhabitants of Vortis. Removing the Menoptera bodies from two of the robot Zarbi, the Doctor and Gordon crawl inside. The Doctor determines how to control them. Using his radio, he sends a powerful signal to find the missing crewmembers. Instead of raising the crew, the signal stops the Zarbi in their tracks. When the Zarbi began moving again, the Doctor tells Gordon that the radio almost gave them away. Gordon realises that the other crew members' radios likely caused their capture.
The Zarbi, now all moving in one direction, sweep the Doctor and Gordon along into a large, squat anthill containing great machines and engines manned by Zarbi workers. The Doctor and Gordon arrive at a great, underground amphitheatre. At its centre is the Zarbi Supremo, three times the size of an average specimen. Standing before the Zarbi Supremo are the six missing crew members from the Solar Queen and a party of Menoptera, all with collars around their necks holding them motionless. Slowly, the Doctor guides the two robot Zarbi through the crowd to the front of the throng. The lead Menoptera tells the Zarbi Supremo they will not help in his invasion plans of Earth. They will go to war against the Zarbi to stop them. After the Zarbi Supremo kills the lead Menoptera, the Doctor and Gordon use their robot Zarbis' mandibles to remove the collars from the crew members' necks. The Doctor calls on the crew members to shoot the Zarbi Supremo. While most of the bullets miss or bounce harmlessly off, enough find their way through to kill the Zarbi Supremo.
Once the Zarbi Supremo dies, the rest of the Zarbi wander around the chamber, paying no attention to the humans and Menoptera. Once freed from their collars, the Menoptera tell the Doctor that over the years, the Zarbi evolved an intelligent leader who dreamt of conquest. The Menoptera built their first weapons to fight them and had many robot Zarbi throughout the amphitheatre. The Doctor and crew of the Solar Queen return to check on Gordon's father. Although still unconscious, he is doing better. One of the crew verifies Gordon's story that Vortis is near Jupiter's moons. One of the Menoptera explains that great engines was built by the Zarbi to guide their world in search of a green, wet world like Earth.
The Menoptera fly the Doctor back to the TARDIS and say goodbye, telling him of their legends about him and his ship.
- This story was included as a special audio feature on the The Web Planet DVD, and was read by William Russell.
- As was almost universally the case in 1960s and 1970s prose fiction, the Doctor is referred to interchangeably as "Dr. Who" and "the Doctor".
- Indication is given that the Doctor is from Earth. However, the editors make very clear a few stories later that the Doctor is in no way from Earth, though he likes to lie that he is.
- This is the Doctor's second visit to Vortis. His last visit had been in PROSE: The Lost Ones, and he would next visit in TV: The Web Planet and COMIC: On the Web Planet. The Second Doctor returns to Vortis in PROSE: Twilight of the Gods. The Fourth Doctor returns to Vortis in COMIC: The Naked Flame. The Fifth Doctor returns to Vortis in AUDIO: Return to the Web Planet.