Agent Lockwood is an FBI informant handler most notably assigned to the operation to take down the Earth Defenders Group eco-terrorists. Lockwood was first the handler of Haley Kerns when she turned in her drug dealer ex-boyfriend, Zander Owens. Her not being the only suspect in prison led Owens to know Haley ratted him out, leading Owens to kidnap, rape, and brutalize her, shaving her head out of revenge. This was to the chagrin of the SVU detectives, especially since EDG brainwashed her and the feds blackmailed her with penalties to stay to the directive. (SVU: "Informed")
When Haley was killed to stop an attack she was a part of and Detective Benson took her place, Lockwood was her handler as well, with Dean Porter being her liaison. When the terrorist they were after was already in a Montreal prison, Benson was relieved of her assignment and returned to Manhattan. (SVU: "Infiltrated")