NCIS: Season 3, Episode 8

3 - 8: Under Covers

When it is discovered that two married assassins, who were fatally wounded in a car crash, were planning an assassination at the United States Marine Corps Birthday Ball, Gibbs sends Ziva and Tony to pose as the married assassins in order to find out who the couple had planned to assassinate and who had hired them. After the team finds out that the couple were expecting a baby and may have been planning to retire, they realize that the assassination plot could have been a set-up and that the married assassins were potentially the real targets. Meanwhile, an attraction between Tony and Ziva surfaces.