Agent Carter is back in action.

'Agent Carter' Season 2 Spoilers: New Female Villain Announced, Is She Masquerading As Wendy Fallon?

The ABC series will return for its second season this winter, and Monday marked the first day of filming for the cast and crew.

"3am wake up call. Time to go to work," Hayley Atwell (Peggy) tweeted in the early hours of Monday morning. "‪#AgentCarter season 2 filming begins!"

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Agent Carter burst on to the scene last January, expanding upon Marvel's similarly titled One Shot. The series revolves around Peggy, who first appeared in Captain America: The First Avenger. Now working for the Strategic Scientific Reserve in post-war America, Carter spent her first season working to take down Leviathan with Howard Stark's (Dominic Cooper) loyal butler Jarvis (James D'Arcy).

As season 2 begins, Peggy will swap the Big Apple for the City of Angeles. A new plot is a foot, and this time Carter will have to go up against the mysterious powers of Darkforce and Madam Masque. Capable of becoming a solid, liquid, or smoke, Darkforce has the ability to create new heroes and villains. Unfortunately, the SSR will be at a loss when it comes to understanding this ominously titled enigma.

"It affects different people differently, which we liked, and we liked putting something like that in 1947. And actually, trying to give it a scientific explanation -- what is it? And Peggy wants to know the same thing, what is it?" executive producer Michele Fazekas told Comic Book Resources.

Find out more when Agent Carter returns to ABC in 2016.