Codebreaking at Bletchley Park in "The Bletchley Circle." (Credit: Courtesy of ©World Productions 2013)
Code-breaking at Bletchley Park in “The Bletchley Circle.” (World Productions)

“Mad Men” returns on Sunday, careening toward the end of the 1960s. But as much as it has been rewarding (and sometimes frustrating) to watch Peggy Olson (Elisabeth Moss) grow in professional confidence and power over the course of that decade, I am also excited for the second season of “The Bletchley Circle,” premiering on PBS. That show, which set its first season in 1952, explored the sorts of tensions that would make Peggy’s rise feel so exhilarating. Following a group of women who worked together as code-breakers at Bletchley Park in Britain during World War II and restart their friendship years after their service ended, “The Bletchley Circle” examines a moment when the gains women made in wartime were rolled back, denying them intellectually stimulating employment and prestige in the communities they worked so hard to impress.

War “can be damaging or harrowing, but also fulfilling, and giving opportunities,” executive producer Jake Lushington told me when we spoke in January, emphasizing that it was not only women who struggled with the aftermath of World War II. Susan Gray (Anna Maxwell Martin), who brought her old friends together to investigate a murder in the first season, was valued at Bletchley for the focus her Asperger syndrome gave her, but now keeps house for her husband, Lushington pointed out. Susan’s husband, by contrast, has neither her neurological gifts nor her deficits, but still struggles to adjust to the monotony of a desk job.

“I imagine everything felt like it was in technicolor in terms of the stakes,” said Hattie Morahan, who joins “The Bletchley Circle” this season as Alice, whose wartime love affair both liberated her and left her unwilling to conform to the expectations of the civilian life that she returned to. “Reading about the lives at Bletchley Park, it feels like there was this liminal space where romance out of the conventional rules of society could blossom because there was secrecy, because people knew not to ask questions, and a very heady atmosphere happening at the time. ”

But Lushington and his characters agree on the unique situation of women, who made advances only to be excluded from rewarding jobs they had performed well, and to be faced with rigid expectations for keeping up appearances even when rationing continued after wartime.

Rachael Stirling plays Millie, an unmarried woman working legally as a translator — and illicitly as a seller of stockings and lipstick — who clings to her independence despite its costs. She said she thought it was no mistake that women’s liberation followed the experiences of the war.

“It’s not a coincidence that shortly after this, the ’60s hit, and therein began the rebellion by women, on behalf of women, for their own sake, as a direct result of the oppression you see in this episode,” she argued. But the characters on “The Bletchley Circle” are the precursors to that conversation, Stirling suggested. “There is a sense of injustice, but it’s not an abnormal injustice, it’s an accepted injustice … Post this period, women must have started talking to each other about how frustrated they were … At that point, we didn’t sit around the table in the library, we don’t gang up and go, ‘Argh, men.’ ”

Instead, the women work to solve crimes that are mishandled by large police bureaucracies. (Lushington emphasized that some individual police officers were sympathetic and helpful.) This year, their cause is Alice, who has been imprisoned for the murder of her wartime lover, and it is Jean (Julie Graham) who mobilizes the others to reexamine her case when Alice will not speak on her own behalf.

“They do this, because like the war, this needs to be done,” Lushington said. The way his characters approach the world is to say: “We’ve had an experience of solving things and being valued that we’re not going to let go of.”

That same quiet commitment to the work would make Peggy Olson a star on another continent a decade later. And as “Mad Men” comes to an end, one of the best and most entertaining ways to explore the themes it has raised for seven seasons is to look back in time to the struggles and friendships of the women of “The Bletchley Circle.”