"And just to add one further element of terror, reports say that Riggs has discovered two CIA undercover agents working in his midst. One of the agents is Susan Riker. She is reportedly chained to a jet fuel storage tank that might be wired with a time bomb. You don't like this information one bit. Especially since Susan Riker happens to be your fiancee."
--Terminal Terror documentation
Susan Riker is a CIA agent and Nick Hunter's fiancée in Terminal Terror (1994). Before the start of the game she is captured by the terrorist Bruno Riggs whilst working under cover, and thus rescuing her is one of Nick's and therefore the player's motivations.