Don Seong is a Korean immigrant and administrative director at Foster Medical Research Group. His wife, Young-Hee is befriended by Elizabeth Jennings in her "Patty" disguise as a means of gaining access to him since he can provide the "Level 4" security code that William needs to obtain deadly pathogens.

"Patty" drugs and manipulates Don into thinking he has slept with her, and later, that she has become pregnant. Don tells Patty to get an abortion. Later, disguised as her family, "John", Gabriel and another agent visit Don at work announcing Patty has killed herself, and demanding money to pay for funeral expenses. When Don leaves with "John" to retrieve the money, Gabriel and the agent copy his computer discs and gain the access code.