Kritakh

Kritakh was a Zygon. He and Torlakh were sent to Earth to make it more habitable to Zygons by releasing nuclear waste into the atmosphere over a hundred year period. Kritakh took the form of the human electrician Michael Kirkwood as part of his cover. However, Kritakh forgot his true identity over time and believed he was Kirkwood. As Michael, he became romantically involved with his psychiatrist Lauren Anderson, a human who was later turned into a Zygon herself by Torlakh. Together, they found the real Kirkwood and brought him to a hospital to recover, with Lauren killing Torlakh before he could poison Earth. (HOMEVID: Zygon: When Being You Just Isn't Enough)