- "You're leering at Langer. You're Langer-leering."
- —Anthony DiNozzo upon noticing Ziva David's attraction to Langer in the Season 5 episode, Tribes (episode)
At some point, Langer moved to the FBI until few years later, while he was with the FBI, Langer was reunited with Gibbs when he worked with Gibbs and his team on a case involving the murder of a Muslim marine.
Langer was one of three NCIS agents (the other two were Lee and Keating) suspected of being a mole and leaking US military files. After the original agents, Anthony DiNozzo, Timothy McGee and Ziva David were reassigned elsewhere, the trio were placed on Gibbs's team in order to bring them under closer scrutiny and determine which one of them was the mole. Langer was killed by the real mole in the agency: Michelle Lee, who accused Langer of being the mole and shot him, claiming self-defense for her actions.
Later, in the episode, Cloak (episode), Agent Lee admitted under questioning by Gibbs that Agent Langer had been innocent and was not engaged in espionage. Gibbs, however, was already convinced of Langer's innocence, having previously placed Langer's old FBI ID on a bar wall dedicated to fallen officers and agents.
Agent Langer was referenced during the sixth season episode, Collateral Damage (episode) through the use of flashbacks.