Melinda McGraw, Mark Harmon

NCIS' Leroy Jethro Gibbs is a man of few words and many wives. And this November, viewers are going to meet another former Mrs. Gibbs, TVGuide.com has learned exclusively.

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Mad Men
mistress Melinda McGraw has been cast as Diane, one of the three (redheaded) women Gibbs (Mark Harmon) married after his first wife was killed. Fans of the show will recall that after Diane split from Gibbs, she also married his friend and colleague, FBI Agent Tobias Fornell (Joe Spano), who will also return for the episode.

Although Fornell had a daughter with Diane, both men have not-so-fond memories of her. (She cleaned out both of their bank accounts after their respective divorces.) Diane comes back into the men's lives when her latest husband gets tangled up in a joint NCIS-FBI investigation. Fittingly, the episode is titled "Devil's Triangle."

"Imagine being the ex-wife of both Gibbs and FBI Agent Fornell," executive producer Gary Glasberg tells TVGuide.com "Melinda McGraw brings enormous heart, humor, bite and edge to a character we've known about for years, but haven't spent much time with. This is gonna be fun!"   

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McGraw, who has appeared on such shows as Desperate Housewives, The West Wing and The X-Files, notably portrayed Bobbie Barrett, one of Don Draper's mistresses in Mad Men's second season. She also recently recurred in the second season of TNT's Men of a Certain Age as a love interest of Scott Bakula's Terry.

McGraw's episode is slated to air in early November. NCIS airs Tuesdays at 8/7c on CBS.