Johann "Dr. Ivchenko" Fennhoff

Dr. Ivchenko is discovered imprisoned along with Nikola inside the Leviathan facility. He explains that Leviathan has acquired stolen schematics for a weapon and is forcing Nikola to construct it. Ivchenko identifies himself as Nikola's psychiatrist and explains that his purpose is to help Nikola manage the extraordinary way in which he perceives scientific information.

Ivchenko presents himself as a calm, rational physician and appears to regard Nikola as a gifted but psychologically burdened man rather than a conventional mad scientist. His explanation gives Peggy and Thompson important information about Leviathan's plans and establishes the connection between the organization and the stolen Stark technology.

Ivchenko presents himself to the SSR as a frightened Soviet psychiatrist with limited knowledge of Leviathan. In a flashback, he describes being recruited after witnessing Leviathan murder a man who refuses its offer. He explains why women make effective covert operatives, telling Peggy and the SSR that they are often underestimated and can pass through a man’s defenses.

Behind that cooperative façade, Ivchenko communicates with Dottie through Morse code and sends her a new directive to kill Peggy. He probes Dooley’s marriage to create emotional leverage, then manipulates Yauch into revealing information about Stark’s weapons and the SSR building. Ivchenko sends Yauch away under post-hypnotic instructions that lead him into traffic, removing a witness and proving that his polite demeanor is just another weapon.

Johann Fennhoff has been operating inside the SSR under the identity of Dr. Ivchenko. His abilities are demonstrated through a flashback to 1943, when he helps a wounded Soviet soldier endure an amputation without anesthesia by placing him into a hypnotic fantasy. Fennhoff manipulates the soldier's perception so that he experiences the operation as a peaceful game of chess with his mother.

In present day, Fennhoff communicates with Dottie Underwood through Morse code from Dooley's office inside the SSR. After Peggy discovers the communication, Fennhoff uses his hypnotic abilities on Roger Dooley and directs him to retrieve one of Howard Stark's confiscated weapons. He then places an unstable explosive Stark device on Dooley while keeping him under hypnosis and uses Dooley as a distraction while he carries out the next stage of Leviathan's plan.

Fennhoff is revealed to be the man operating under the identity of Dr. Ivchenko. He has been pursuing Howard Stark because of Stark's connection to Midnight Oil and the battle of Finow. Fennhoff explains that he witnessed the effects of the chemical while wearing a gas mask and later found his brother dead with severe injuries. He blames Stark for creating the substance and intends to punish him rather than simply kill him.

Dottie creates a diversion during Howard's public appearance and has Howard kidnapped. He takes Howard to a Stark aircraft hangar and uses hypnosis to manipulate him into believing that Steve Rogers has been found alive. Fennhoff attempts to make Howard release Midnight Oil over Manhattan. He also attempts to hypnotize Sousa during the pursuit, using Sousa's wartime injuries and feelings about Peggy against him. Peggy breaks Howard's conditioning, while Sousa resists Fennhoff's commands (with the use of earplugs) and helps capture him. Fennhoff is imprisoned and later approached by Dr. Arnim Zola in his cell.