James L. Lennox was an undercover CIA agent who tried to infiltrate Enzo Markovic's lab. He was captured by him and Markovic became a doppelganger of Lennox himself. Lennox was also engaged with Emma Wallace, who was killed by Markovic.
Lennox was captured off-screen and tortured for four weeks by several of Markovic's doctors. Unbeknown to Lennox, his fiancee was sleeping with a faux Lennox and wound up getting captured by him as well, only to be killed after she was strapped with several blocks of C-4.
After interrogating Arden Jezek, Sydney and Vaughn located Lennoz at the bottom of Markovic's office, where he was being tortured by the doctors. While leaving, Sydney and Lennox were ambushed by some of the guards, but Lennox risked his eyesight to save Sydney and shot the assailant in the back. While heading back to the CIA Headquarters, Sydney told Lennox that his fiancee was dead.
Lennox arrived to the CIA HQ and confessed that they were a part of Merkovic's entourage and that Wallace was her fiancee before departing back to his home. Sydney came over and found Lennox in a drunken state, upset about his fiancee's death. Sydney also confessed about Danny's death and how both of them had lost something they loved. Lennox began to kiss Sydney, but realized he made a mistake and told her to leave...just in time for CIA agents to appear and arrest Lennox.
Lennox was soon released from holding when they figured out Markovic made himself look like Lennox, which was why Emma didn't contact anyone. The two traveled to Poland to destroy Project Helix, but Lennox found out that he wasn't the only one who had been copied. Pretty soon, Markovic arrived saying he was the real Lennox and Sydney handcuffed Lennox to the wall, unaware that it was Markovic who contacted her.
After escaping, Lennox and Markovic foud each other and held their guns at each other, trying to coerce Sydney that one of them was Markovic. With no other way of proving who was who, Sydney threatened to blow up Project Helix, which revealed the true Markovic. Lennox shot him twice and Sydney blew up the container.
Lennox and Sydney returned to the CIA, where he announced he was on a four week vacation. Lennox told Sydney he was going to Fiji because both Wallace and Lennox would spend their honeymoon there, and left.