NCIS: Season 3, Episode 16

3 - 16: Family Secret

An ambulance explodes and practically disintegrates the body of William Danforth, a deceased Marine it was carrying. A DNA analysis performed on a piece of body tissue informs the team that the body does not belong to Danforth. The team suspects that Danforth's best friend, who was a bomb expert, helped Danforth fake his death in order to leave the Marine Corps. When Danforth is discovered to have been a recipient of a donor organ, the team realizes that the body may in fact be Danforth's after all, and they are forced to examine reasons as to why someone may have wanted to disguise that the body was his.