William Ryan was a Colonel in the United States Marine Corps and a former commanding officer of Marine Gunnery Sergeant-turned-NCIS Special Agent Leroy Jethro Gibbs.
NCIS Season 1Edit
He appeared in episode Enigma where he asks Gibbs for help as he believed that there was a conspiracy going on. He was aided by Lt. David Cameron, a man who appeared to have died previously, which Gibbs claims to be true as Cameron died in his arms. When Tobias Fornell appeared at Ryan's lair while he was showing Gibbs several weapons he and Cameron have been storing there to fight the conspiracy, Ryan and Cameron leave to confront Mike Granger, whom they believe to be part of the conspiracy. However, it is finally revealed that Cameron was indeed dead and Ryan had been following the instructions of a hallucination, believing in a conspiracy which actually didn't exist at all and was also a mere product of his fantasy. Realizing what he did, he tried to shoot himself, but Gibbs convinced him not to, so Ryan fell into his arms, sobbing that he doesn't understand. In the end, he is seen locked up in an asylum where he stares at the window, repeating that he doesn't understand.