Nathan Stark (Ed Quinn)Nathan Stark is a Nobel prize winning mathematician who is also knowledgeable in many other scientific fields.Although it is said that with his mind he could've been a huge benefit in working to further science, Nathan instead chooses to work as head researcher for Global Dynamics.He is the estranged husband of Allison Blake and may still have feelings for her.Nathan is handsome, charming, and very private. He and Jack often disagree but have a mutual respect for one another's skills.He is often a man of action as opposed to talk.