Albert Mertens was the lead professor who worked alongside his mentor, Gerald Bull on the "Babylon Supergun." Before the weapon is finished, Gerald Bull is assassinated and Mertens is committed to a mental institution. It is unknown how he escaped, but speculations points at terrorist organization The Shadows. He is recruited in the organization to work on the "Babylon Phoenix", a modified version of the Babylon Supergun. After sharing a sentiment that Baghdad should not be the target for the Phoenix, he decides to betray his superior, Nasir Tarighian, and instead target Jerusalem. He was likely killed in the airstrike against the facility, minutes after Splinter Cell operative Sam Fisher was able to send pictures of the weapon back to Third Echelon.