Dr Fendelman was a wealthy businessman who discovered "Eustace", a humanoid skull that pre-dated humanity by eight million years. With his team of Maximillian Stael, Thea Ransome and Adam Colby, Fendelman studied it at Fetch Priory.
According to Thea, Fendelman was one of the "authentic geniuses" in the field of electronics until he developed his interest in the origins of man. Colby took a different view, suggesting Fendelman's genius was ended when he "flipped his lid." Data from his work led the doctor to an excavation site in Kenya, where he found Eustace. He assembled his team of Stael, Colby and Ransome, with the offer of unlimited funds.
Fendelman conducted secret experiments with a time scanner, with only Stael assisting him in this. The Relative Continuum Displacement Zone created by the operation of this drew the Doctor's TARDIS and, knowing this zone could be destabilised and result in a "direct continuum implosion", the Fourth Doctor and Leela came to Fetchborough in search of the source.
In July 1977, Colby told his colleagues, while they were gathered in the priory's kitchen, that he had found the body of a hiker in the woods nearby. Fendelman argued that, given the belief that these woods were haunted, this would lead to unwanted attention as a result of publicity. He convinced Colby that it was best to move the body, reminding him that he wouldn't want his Nobel Prize to be jeopardised. Thea was unmoved, and said that it was illegal. Fendelman replied that it was a "small deception only", and Colby agreed that it wouldn't make much difference. Speaking to Stael alone, he told him to "get on to London" and tell Hartman he wanted a security team at the priory in two hours. He also asked Stael to perform a post-mortem on the hiker's body.
This done, Stael went to Fendelman in his lab. The doctor was working, and told him "if we can get a visual representation of this area here, then we shall see the living owner of that skull". Stael informed him of the results of the post-mortem - the body was decomposing already, and appeared to have had all the energy drained from it. Fendelman told him to dispose of the body and warned that nobody was to know of this.
Annoyed by the limitations on access, requiring the permission of Fendelman to come and go from the priory, Colby went to see Fendelman in his lab. The doctor asked if his machines impressed Colby, who replied that "I always say if you've seen one jukebox, you've seen them all." Fendelman explained how it was his work with this equipment that led to the discovery of Eustace. He then explained his current work, leading Colby to tell Thea when they were alone that he was "crazy as a bed bug", adding that "he actually believes that he can see into the past with that electronic fruit machine he's got down there."
The Fourth Doctor came to the priory and attempted to explain to Colby the cause of the happenings there, a second man, David Mitchell, head of the security team, having died, and Thea having collapsed with Fendahleen appearing on her prostate form. Fendelman entered the kichen, where they were, and the Doctor spoke to him, saying "Doctor Fendelman, I presume. Is that really your name, Fendelman?" and asked him to dismantle the scanner and perform some tests on Thea, beginning with an x-ray of her skull. Instead, Fendelman ordered that the Doctor be locked up, saying he suspected him of murder. Colby said he would now call the police, but, as he left, Fendelman asked how he would explain having not contacted them before.
After finding that the telephone had been disconnected, Colby again confronted Fendelman and this time accused him of being mad - cutting their communications off and surrounding them with guards. Fendelman then explained his theory about Eustace: that he believed the skull to be of extra-terrestrial origin. In the kitchen, with Thea present, he added to this, saying that man did not evolve on Earth, but from this alien species. He told Colby that, with his scanner, he had traced the moment of death of this "alien traveller" and, at that moment, the scanner showed an enormous surge of power, which was what had first attracted his attention. Where this power was stored, he explained, he had not discovered until he x-rayed the skull. Fendelman admitted to his secret experiments with Stael and explained that he believed their importance made this necessary, adding "and now we have these murders and this mysterious intruder." Saying she felt tired, Thea left them, and Fendelman told her he would ask Stael to look in on her later. With her gone, he said to Colby that he believed the Doctor had been spying on them.
Fendelman showed Colby the x-rays, which showed a pentagram on the cap of the skull. The doctor said this was part of the bone structure, and that he believed it to be a kind of neural relay, where the energy was stored. Fendelman told Colby this energy could only be released by advanced technology, and Adam realised his theory - that this would act as a signal to their alien predecessors. Thus, as Fendelman put it, humanity would meet "its destiny".
Colby noted that Fendelman had been running the scanner for over ninety-eight hours, and the doctor replied that it had been "a joy". Colby queried why evidence of alien origin hadn't been found before, and Fendelman told him it was because they hadn't been looking and that, without the scanner, this wouldn't have been discovered. Colby told him it was illogical conclusion. Fendelman told him he would see, and added "I have already reprogrammed the computer. This time it will give a visual interpretation of what the scanner picks up. On this screen, Colby, you shall see the true genesis of homo sapiens."
As the machine was working, Stael entered and, threatening them with a gun, demanded that it be turned off. Fendelman asked Max if he had lost his mind and refused to comply. Colby did, and turned the scanner off. Stael took Fendelman and Colby to the cellars and tied them to separate pillars. The doctor asked how long he had been planning this, and Max replied that it was ever since Martha Tyler's visions had begun to come true. Fendelman berated him, saying "visions? Oh, come now, Max. You have a first class brain. Use it." Colby disagreed, labelling Stael an occult freak. After listening to Adam's further insults, Stael told him he would enjoy his terror and left. Colby asked if the security guards could help, but Fendelman told him they were to take orders from Stael in his absence.As Stael began to prepare for his ritual, connecting a power source to Eustace, Fendelman told Colby that he believed he knew what Max planned. With his coven gathered, Stael declared that the waiting was over. Fendelman shouted at him, telling him not to do it. Colby told the doctor to "shut up" and let Stael electrocute himself. But Fendelman continued, yelling "he will kill us all. Listen to me, all of you. He is a madman!" He warned that Stael would plunge everything into "chaos and death." Again, Colby told him to be quiet. Fendelman replied that he did not understand, and he himself knew now what would happen. He spoke to Stael, saying "the Doctor asked if my name was real. Fendelman. Man of the Fendahl. Don't you see? Only for this have the generations of my fathers lived. I have been used! You are being used! Mankind has been used!" Stael walked over and shot him in the head.
After his death, one of the theories the Doctor considered for the origins of man was that "the Fendahl fed into the RNA of certain individuals the instincts and compulsions necessary to recreate. These were fed through the generations till they reached Fendelman and people like him." (TV: Image of the Fendahl)