Matthew Weiner's series finale of Mad Men is a heavily guarded network secret, though it looks like at least one person outside the AMC circle knows how the program will end.

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Star Jon Hamm, who's portrayed the iconic Don Draper for seven seasons, revealed to Us Weekly on Friday that as careful as he is to reveal spoilers, there's one person he can't lie to: his girlfriend.

"Oh she knows," declared Hamm, referring to his longtime girlfriend and fellow actress and director Jennifer Westfeldt.

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"I tell her everything!" added the 43-year-old actor. "I tell her everything and she definitely knows."

Known for directing and starring in the comedy-drama Friends With Kids, 44-year-old Westfeldt has been with Hamm for over 15 years, and he trusts her completely. "She won't tell anyone!" he insisted.

Nonetheless, Hamm won't be revealing any details publicly about the drama, which airs its final episodes in just a few months. "I'm pretty good at keeping it secret by now," said the actor. "I'm looking forward to it, I think we'll have a good time."

The cast of the game-changing drama have spent nearly a decade under Weiner's anti-spoiler training, and with Westfeldt not talking, fans will just have to wait to see what will happen when the program returns next year. As the first half of the season proved over the summer, anything can happen and no one is ever really safe. Will Draper live? Will he die? Either is possible when all is said and done.

Mad Men returns to AMC to finish out its seventh and final season in 2015.

Tags: Mad Men AMC television