Agent Carter 2×04 provides one of the series’ most thoughtful and potent installments by illustrating Peggy’s history — and that of her nemesis Whitney Frost.

The episode, titled “Smoke and Mirrors,” has a few motions of plot on its mind — Peggy and Sousa crack her would-be assassin, while Whitney experiments with her powers. But the primary concern is in the episode’s gauzy and gloriously surprising flashbacks, and how they shape the present.

Peggy’s childhood identity as a brave, imaginative girl who wanted to slay dragons (and rescue princesses) is easy to match with the Margaret Carter we know and love. But it’s her adulthood that proves rather shocking. The Peggy of Bletchley Circle is a woman, or perhaps a girl, who had accepted the classic restrictions of her gender. The accomplishments of her mind were secondary to the diamond ring on her finger; she did not consider accomplishments of her body.

Hayley Atwell does remarkable work in Agent Carter 2×04, reinventing her character all over again. Marvel fans have seen her as a fierce fighter, a wizened leader, an elderly woman who has lost everything, but we have never seen her like this. Demure, unassuming, modest, even shy — this old Peggy is brand-new, and Atwell plays her with a wide-eyed transparency that is both authentic and deeply startling.

It’s notable (and an important contrast to Whitney’s story) that Peggy discovers her true self because of a man. Throughout her life, Peggy’s brother Michael was the one who dreamed of a life beyond her prescribed borders — and begging her not to let expectations ‘drum her dreams out of her.’ Tragically, it’s only Michael’s death that inspires Peggy’s internal alchemy, transforming her from a weeping woman in a wedding dress to a determined member of England’s Special Operations.

And as we know, that transformation paid off. In the present day, Peggy skillfully manipulates Rufus Hunt into disclosing information about Calvin Chadwick and the “Council of Nine.” And when the Council turns out to have fingers far closer than Peggy anticipated — specifically in a quietly threatening Vernon Masters — Peggy sends her Hunt straight to the Chadwicks, wearing a not-so-well-concealed bug.

But Peggy’s well-crafted plan contains one minor flaw: She doesn’t really know Whitney Frost.

Which is a shame, because Frost is becoming one of the most fascinating and idiosyncratic characters on this season of Agent Carter. She is brilliant and nasty in equal measure, dedicated to science beyond anything else – even her own safety. The world (and her own husband) view Whitney as a figure and a face; Whitney views herself as a mind. So what if her experimentation leaves black cracks of void curling across her face? Her looks are no loss compared to what she has gain in knowledge… and in power.

In exposing Whitney’s history, “Smoke and Mirrors” also unveils a fascinating contrast to Peggy’s life. Peggy had accepted her demure attitude and its domestic trappings until she was given strong enough cause to reject them. Now, as we know, she creates her own power on her own terms, largely in defiance of societal expectation.

But Frost does the opposite. Finding no purchase for her goals, she takes her mother’s advice and adopts the demeanor of a dim, beautiful actress. Playing to expectations has transformed Agnes Cully into Whitney Frost, but her face and her fame have restricted her… until she was embraced by Zero Matter.

Whitney’s experimentation with the extra-dimensional material tells us a lot about Frost, but rather less so about Zero Matter itself. That task is left to the increasingly woebegone Jason Wilkes, who finds himself drawn into its leaching void, but still manages to steal a smoldering moment with Peggy. (Much to the frustration of Sousa, because unless your name is Ana Jarvis, no one on this show really knows what they want.)

Regardless, Peggy’s bug does create a major crack in her investigation — though not at all what she expected. After hearing of Hunt’s confessions and facing the threat of blackmail (for what, we don’t yet know) Whitney literally takes matters into her own hands. Peggy, Jarvis, Wilkes, and Sousa are all left listening in shocked confusion to Hunt’s dying, choked-off shriek; Calvin Chadwick experiences an entirely new level of revelation.

For the first time, Chadwick truly sees his wife. Her ignored capability, her concealed genius, her seething power is now impossible to ignore – and there’s the small issue of the Zero Matter. The hidden woman now brutally revealed, and accordingly, we suspect that revelation will take center stage in a previously shrouded season.

Peggy knows about Whitney. Whitney knows about Peggy. Soldier and scientist, heroine and villainess, dark and light, are finally primed for conflict. What’s the phrase?

Oh yes. Tick, tick, tick… boom.

What are your thoughts on ‘Agent Carter’ 2×04?