Yvonne Strahovski and Cheryl Ladd

As NBC's spy caper Chuck heads toward the series finale, the final batch of shows will focus on Chuck and Sarah's past. On the emotional December 30 flashback episode, we'll finally be introduced to Sarah's mother, Emma, played by former Charlie's Angels star Cheryl Ladd (pictured, with Yvonne Strahovski).

"Sarah and her mother share a mystery that has forced them to be apart," says exec producer Chris Fedak. "After this, you will know Sarah as a different character."

Expect Chuck (Zachary Levi) and Sarah to discuss baby making and suffer a great loss just before the two-hour January 27 finale, which features the return of Chuck's mom (Linda Hamilton), a private jet, a grand concert-hall sequence and visits to the French Riviera and Berlin.

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