NCIS' Gibbs (Mark Harmon) won't have to wait much longer for his final showdown with the man who killed his ex-wife Diane (Melinda McGraw). In fact, the conflict between Gibbs and Sergei Mishnev (Alex Veadov) "comes to a head" on Tuesday's episode.

"It's kind of been percolating under the surface for Gibbs, and clearly his wheels are turning and he's brooding," executive producer Gary Glasberg tells TVGuide.com. "He's thinking and he's plotting and he's planning. ... As we all know, Gibbs isn't one to just sit back and let things happen."

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But even if Gibbs is able to get his revenge, it won't bring Diane back to life. And unfortunately for Gibbs, the repercussions of her murder will play out for a long time to come, for both Gibbs and Fornell (Joe Spano).

"At the end of the day, Gibbs feels a certain responsibility for what happened," Glasberg says. "Whether that's accurate or not, he's carrying that around with him, and Fornell is carrying that around with him. ... There are really some brilliant moments between Gibbs and Fornell. I couldn't be happier with the performances that they gave. It's a touching, really strong episode."

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