Hans was a KGB agent, motivated by his disgust with South African apartheid and America's support of it. He was an economics graduate student from South Africa working in the US as a Teaching Assistant.
In November 1982, Elizabeth teaches Hans surveillance techniques, such as tailing a car without being noticed, ("EST Men") and picking up details. ("Open House") He killed Todd, one of his fellow South African students, after he saw Hans during one of the operations. He assists Philip in keeping Martha under surveillance.
In February 1984, Hans was part of a crew that included Philip and Elizabeth, who exhumed William's body to obtain a Lassa virus sample. During the transfer of the virus to the container, he tripped and fell into the hole, cutting himself and becoming exposed to the virus. Knowing that he would contract Lassa fever and suffer a horrible death, Elizabeth shot and buried him along with William's body. ("Amber Waves")
At the time of his death, Elizabeth said Hans had not seen his parents in several years. His sister had been planning to visit him in the US in a few weeks. ("Pests")