Fetch Priory was an priory, near Fetchborough, England. It was used as a research centre for Dr Fendelman and his colleagues, Maximillian Stael, Adam Colby and Thea Ransome, who were studying the mysterious skull, Eustace. Martha Tyler worked as the cook at the priory.
In his lab, Fendelman used a time scanner in experiments kept secret between him and Stael. While the scanner was active, a hiker in the woods adjacent to the priory was attacked and killed by a Fendahleen. Fendelman asked Stael to have armed guards posted and to conduct a post-mortem on the body.
After the Doctor's TARDIS was dragged towards a Relative Continuum Displacement Zone, the Fourth Doctor and Leela travelled to Fetchborough in search of the source. They were told by Ted Moss about Fendleman's work at the priory.
Thea activated the time scanner, finding herself drawn to the machine. In the priory kitchen, the leader of the security guards, David Mitchell, was killed by a Fendahleen. Thea was again drawn to the scanner and, while in the lab, Stael approached her and told her she was the key to his power - his coven intending to use her in a ritual that would give Stael great power.
Having used a gun to take them prisoner, Stael took Fendleman and Colby to the priory cellars and tied them to pillars. His coven then assembled for the ritual, with Thea at its centre. Fendelman guessed Stael's intent and told him humanity had been used. Stael, angered, shot him dead. The skull was coupled to the time scanner, and Thea was transformed into the Fendahl core. She then set about killing the members of the coven, including Ted Moss.
A Fendahleen appeared in the priory and the Doctor shot it dead using a rock salt-filled cartridges. The Doctor and Leela then freed Colby. Stael, having looked at the eyes of the core, could not move. He asked the Doctor to hand him his gun, which he did, and he committed suicide. Jack Tyler and Leela used the rock salt from the charms given to them by Martha to kill a further Fendahleen then appeared to them in a corridor of the priory. As Jack looked at the core's eyes when it appeared alongside the creature, he could not move, and Leela had to forcefully take the gun from him to kill the Fendahleen.
After Martha Tyler brought him vials of salt, the Doctor instructed her and Jack to return to their cottage. He asked Colby to give him and Leela enough time to get to the cellars, then to activate the scanner for two minutes to distract the Fendahl while he took the skull. After a further three minutes, a controlled explosion he had rigged would go off and the priory would be destroyed, so the Doctor told Colby to ensure he was clear.
In the cellars, Leela and the Doctor threw the salt vials at the core, and the latter placed Eustace in a lead-lined box. They then fled, passing through an apparition of the core as they did so, carefully avoiding its eyes. While in the grounds, they sheltered as the priory was engulfed in flames. (TV: Image of the Fendahl)