William Decker was an NCIS Special Agent.
William Decker was assigned to the mission to assassinate Anatoly Zhukov alongside Jenny Shepard and Leroy Jethro Gibbs. The mission was overseen by Riley McCallister. In the event the mission went south, they were to use the name "Oshimaida" as a codeword to warn the others.
NCIS Season 5Edit
Decker was murdered in "Judgement Day Part 1", killed by assassins working for Svetlana Chernitskaya, former handler of Anatoly and his lover. Sensing his death approaching, Decker put contingencies in place to ensure that his former comrades did not suffer the same fate.
He was found dead in his pool by two boys who tried to play a practical joke on him. At his funeral, Shepard spoke highly of the man. When she went to pay her private respects, she heard a man mention the name Oshimaida, and realized he had been murdered. His girlfriend would communicate, unknowingly, the contingencies to Shepard and former agent Mike Franks: Decker had in his possession an "insurance policy", the key to which he kept at an old diner he had hoped to begin renovating. When they got there, they discovered the key was a series of numbers made out of incorrect dates on several pictures. Shepard never learned what was in the policy, however, as the assassins that killed Decker closed in. She killed most of them before being murdered. Franks quickly killed executed the last assassin, took the key, and left to warn Gibbs.
The Major Case Response Team led by Gibbs managed to identify Svetlana, who Gibbs rushed off to confront. The team, meanwhile, managed to piece together that the insurance policy was hidden in an old NIS case file. When they went to retrieve it, Franks had already looted the box, using his friendship with another longtime employee to gain access to it. Svetlana was killed in a confrontation with Gibbs at the former residence of Jenny Shepard, where Franks ambushed her while she had her sights set on Gibbs. When Leon Vance asked what was in Decker's insurance policy, Franks snidely replied by saying he would leave it for Vance in his will.
NCIS Season 8 Edit
When the Port-to-Port Killer moved on NCIS in "Swan Song", Gibbs called up Franks, and asked him to bring Decker's insurance policy with him in case it might prove useful. Franks revealed the insurance policy was the covert operations history of NCIS and the United States Navy. The box contained dozens of files One of them was Operation: Frankenstein, the program which produced the Port-to-Port Killer Lt. Jonas Cobb. Cobb would kill Franks in a confrontation outside Gibbs's home, leaving the policy in the hands of Decker's one-time partner and friend.
NCIS Season 9 Edit
Gibbs acquired the dossier on the Watcher Fleet's Phantom Eight from the insurance policy, which he would put to use pursuing Jonathan Cole, a rogue operator of the group, and domestic terrorist Harper Dearing.