NCIS: Naval Criminal Investigative Service Episode 1.14 The Good Samaritan

A local county sheriff calls in NCIS upon discovering a murdered lieutenant commander by the roadside, quickly followed by the murder of a civilian contractor two counties over. As the team struggle to find a motive or suspects for either case, another murder occurs; this time a naval aviator. Ducky points out that while the murders appear to follow the same modus operandi and seem to have been carried out by a serial killer, some elements are different, indicating that the murders were not carried out by the same individual. A DNA sample draws suspicion onto the widow of the third victim, but she has an iron-clad alibi, leaving Gibbs with a complex investigation and many loose ends to tie up.