NCIS S07E05:

Code of Conduct

IMDb 7.9 60 min/episodeRelease:2003
A Marine, a practical joker, dies, apparently by suicide by carbon monoxide; Gibbs and company investigate; Ducky rules out suicide, and Abby confirms. Tony starts to arrest the widow, but Gibbs stops him. The gang put the pieces together.
Director: Terrence O'Hara