Professor Eric Stahlman was the originator of the Inferno Project. He was German by birth and had a hard life which made him a hard, determined man. He designed the drill being used, and was the one who convinced the British government to go ahead with the experiment by promising them the pockets of gas beneath the Earth's crust were a vast untapped natural resource. Although Sir Keith Gold was executive director of the undertaking, Stahlman had made certain he, not Sir Keith, would have absolute authority where the drill was concerned.
An argumentative, anti-social man, Stahlman was determined to see Inferno completed ahead of schedule, even if it meant pushing the drilling process past what was considered safe, ignoring even the most basic safety precautions and clashing angrily with anyone who told him he ought to be cautious. He clashed often with Sir Keith and drilling expert Greg Sutton.
When a mysterious green slime was found to have been brought up by the drill, some of it was collected in a jar and shown to Stahlman. When the slime's intense heat cracked the jar's glass, Stahlman acted quickly, grabbing the jar with his bare hands and placing it inside a sealed container. Although he wiped his hands, he was soon infected by the primordial ooze and began the slow process of turning into a Primord. Unlike the others, his transformation took a long time. Mentally, his regression clouded his already impaired judgment and amplified his already bad temper. The more and more he turned into a Primord, the harder he pushed the drill, threatening to bring disaster down on the entire project and even potentially destroy the entire world.
As Inferno reached penetration zero, the heat inside the main drill housing caused Stahlman's transformation to speed up, and he ordered everyone out, then locked himself in, where he covered himself intentionally in the ooze and turned fully into a savage Primord. When the door was finally opened, a fully-mutated Stahlman emerged and attacked the staff, hitting the Doctor with a chair. He was shot multiple times by Brigadier Lethbridge-Stewart before being sprayed by the Doctor with a fire extinguisher, succumbing to the gunshot wounds and perishing. With Stahlman dead, Sir Keith was able to take over and order the drill shut down, with the Doctor carrying out that order before it penetrated the Earth's crust.
Director Eric Stahlman was much the same as his counterpart in the Doctor's universe in terms of personality, except that he was perhaps slightly more reasonable and even-tempered prior to being infected with the ooze. By the time of the Doctor's arrival, he was already regressing into a Primord. Like his counterpart, as his transformation neared completion, he sealed himself in the room with the drill, but unlike Professor Stahlman, Director Stahlman intentionally infected numerous Inferno staff members, including Platoon Under Leader Benton, turning them into Primords like himself. He then became the ringleader of the group of transformed humans.
Although sprayed by the Doctor with a fire extinguisher, he soon recovered, and thereafter escaped from the compound and followed the Doctor and the other surviving Inferno personnel to the power station for the nuclear reactor, where he was ultimately shot by Brigade Leader Lethbridge-Stewart. This too he survived, attacking Dr. Petra Williams while she worked on restoring power to the shed where the TARDIS control console was located, but he was defeated Greg Sutton, who sprayed him for the third and final time with a fire extinguisher. This caused him to finally succumb to his bullet wounds and die.
- In the alternate universe, Stahlman's nametag incorrectly lists his surname as Stahlmann.