Torlakh was a Zygon who was trapped on Earth during the late 20th and 21st century. His superior, Kritakh, and he had been sent to Earth to release nuclear waste into the air, so a hundred years later the planet would be warmer and more hospitable to Zygons. Torlakh was reckless, often trying to avoid duties to "shag" human females. Kritakh would often have to remind him to concentrate on the mission.
To blend in better, Torlakh took the appearance of convict Bob Calhoun. Similarly, Kritakh stole the body of Michael Kirkwood. However, Kritakh soon slipped too far into the persona of Kirkwood. He began to think that he was Kirkwood, and somehow lost all memories of Torlakh or the mission at hand. He began to see a doctor named Lauren Anderson about his visions of being a Zygon. Torlakh stalked the woman, hoping she would help Kritakh remember who he was. He grew angry when she made him worse. Torlakh broke into her house and attacked her.
With her cooperation, Torlakh turned Lauren into a Zygon. He showed her how to shape shift. She betrayed him, reuniting with Kritakh to try to defeat him. They returned to one of the factories they had visited before, deactivating the link in the real Michael Kirkwood and Bob Calhoun, making Bob return to his normal Zygon body temporarily until he regained his apperance as Bob.
Torlakh took revenge on them by taking Lauren's form and going on a killing spree at the hospital she worked at. Lauren, now wanted by the police, met him at her house, only to shoot him, leaving what looked like her body behind. (HOMEVID: Zygon: When Being You Just Isn't Enough)