Stephen had previously given the bracelet to Mary when she was pregnant with Ellie and Sarah reluctantly accepted it, despite it being something Chuck should give to a "real girlfriend.

Mary monitored Chuck's discovery of a safe house in LA, where a menu for a Chinese takeout restaurant provided him and Morgan with clues implicating Volkoff Industries in her disappearance.

During the meeting she provides carefully worded hints that help Ellie locate a hidden message Stephen left for her in the event of his death.

Mary flashed Chuck with a device that apparently neutralized the Intersect, allowing her to capture the pair alongside Tuttle, now revealed as Alexei Volkoff.

However as Volkoff set charges to destroy Stephen's base and intelligence, Mary surreptitiously slipped Sarah a razor to allow them to escape, and asked her to protect her son.

Mary admits Chuck is her son to save his life and Volkoff decides he should join them for Leftovers dinner to meet her family.

When Volkoff destroys the copy hidden in Yuri's false eye and downloads it to another location, Mary retrieves a piece of the micro chip.

A united Team Bartowski retrieves Hydra, arrests Volkoff and frees Mary to be with Ellie when she gives birth to Clara.

With Sarah's life in the balance, Mary sends Chuck out an emergency exit with prisoner Hartley Winterbottom (revealed to be Volkoff's true identity) and false passports, never expecting to see her son again.

Speculation on who would be portraying Mary began immediately after her appearance in the third season finale, and Hamilton's casting was announced during the Chuck panel at Comic-Con 2010.

[11] Josh Schwartz has revealed that when Mary appears in the season four premiere, "Chuck Versus the Anniversary", she will have an "intensity" of which Hamilton is "a natural fit."

Acting as a thorough professional, she shot Chuck (knowing he was wearing a vest) to preserve her cover and later kidnapped him at gunpoint in order to take him to where she stashed the mad scientist for capture.

Nonetheless, she largely remains cold and professional to Chuck, although learning that Ellie was pregnant did have a visible emotional effect on her sufficient to convince her to see her daughter one last time before disappearing again.

However as if to highlight this description Mary also enables Chuck and Sarah to escape behind Volkoff's back, and helped Ellie locate a car Stephen left for her containing some of his inventions, leaving her true allegiances unknown.