Fennhoff was a psychiatrist and leader of the Soviet espionage agency Leviathan in the 1940s. He developed hypnotizing techniques by getting people to focus, which he could use against his enemies, most of whom were instructed to commit suicide. He was able to convince the S.S.R. (without hypnosis) that he was a prisoner of the Red Room in Belarus, going by the name Ivchenko. He insisted Agent Peggy Carter he could help and was taken back to their secret headquarters at New York Bell Co., where worked to undermine the organization within, causing the deaths of Agent Yauch and Chief Roger Dooley.
He then worked with Dottie Underwood to get Howard Stark to fly over New York City and spread Midnight Oil, which would cause an outbreak of uncontrollable violence, but was incapacitated by Agent Daniel Sousa. He was then sent to a prison, where the Hydra scientist Dr. Arnim Zola also resided, telling him to keep positive as they were in an American prison, with America being the land of opportunities. He then proceeded to get Fennhoff to communicate with him writing on paper to further Zola and Hydra's own agenda against the S.S.R.
- Agent Carter