Professor Zaroff was a scientist and leader in the field of producing food from the sea. He disappeared in 1950, having presumably been kidnapped and killed, with the Eastern and Western blocs blaming each other. In actuality, Zaroff had discovered the lost kingdom of Atlantis - either by accident or design - and decided to stay there to further his research, financing a laboratory using the riches of Atlantis. His knowledge led to numerous advances for the sunken kingdom - besides sharing his experience with seafood production, he also enabled the Atlanteans to convert shipwreck survivors into fish people, equipped with plastic gills so that they could survive underwater and collect plankton for the Atlantean citizens. But his most important contribution to Atlantis was his promise that he would lift the continent out of the sea. The Atlantean priests of their goddess, Amdo, proclaimed him to be the prophet that would raise them above the sea; and while some did not like or trust Zaroff, most believed him to be the deliverer of Atlantis. They supplied him with loyal guards and a beloved pet octopus.
While Zaroff was honest about his plans for Atlantis, he neglected to mention his precise means of attaining his goal and the side effects it would have. Rather than physically raising Atlantis, Zaroff intended to bring it out of the ocean by drilling a hole in the Earth's crust and draining the Atlantic Ocean into the planet's core. This would, of course, result in the formation of superheated steam, and the increase in pressure would crack the Earth's crust, destroying all life on the planet if not blowing apart the planet itself. For most scientists, this would be an extremely serious setback, but Zaroff didn't care in the slightest - his goal was not merely to raise Atlantis from the sea; he desired supreme power, which he believed he could achieve through the destruction of the world. Needless to say, Zaroff had also gone quite mad.
Zaroff managed to find a spot on the seabed where the Earth's crust was only fifteen miles thick. In order to drill the hole, he planned to activate his nuclear reactor, and when the desired figure was reached, fission would take place. In order to stop him, the Second Doctor first attempted to kidnap Zaroff, but he escaped by feigning illness, spearing the Atlantean priest Ramo to death when Ramo tried to help him and kidnapping Polly. While Jamie was able to rescue Polly before any harm came to her, Zaroff eluded capture and found King Thous, the ruler of Atlantis. By this point, Thous had come to realise that Zaroff was insane, but when he and his guards tried to stop Zaroff and shut down his project, Zaroff shot Thous with a pistol, and his guards killed Thous' guards.
With his initial plan derailed, the Doctor decided that the only way to stop Zaroff would be to evacuate the lower levels of Atlantis and flood them, submerging both the temple and Zaroff's laboratory. He and Ben infiltrated the generator station, increased the reactor power and broke down the sea walls separating Atlantis from the ocean outside. Meanwhile, the fish people were convinced to start a revolution, which cut off Atlantis' ability to renew its perishable food supplies. Panicked, Zaroff's workers deserted their posts, but even this was not enough to stop Zaroff's experiment. The floodwaters eventually frightened away even the guards in his laboratory, so Zaroff sealed his console off from the rest of the lab with a transparent screen. The Doctor switched off the power to his laboratory, but Zaroff was still confident that he could carry out his plan. What he did not count on was a temple priest hiding behind his console with a knife. Zaroff was forced to raise his screen in order to get to his gun and kill the priest; this gave the Doctor the opportunity to fiddle with Zaroff's console, changing the settings and buying time for the seawater to flood in. While the Doctor and Ben escaped the lab, Zaroff was trapped in it, and when the seawater flooded his laboratory, he was drowned. (TV: The Underwater Menace)
Behind the scenes
- In the novelisation, he is given the first name of Hermann.