In the fourth episode of the second season of Transparent—if you're not caught up, go get caught up and come back to this (spoilers galore below)— Ali visits Grandma Rose in the nursing home. Grandma Rose has dementia, and Ali (played by Gaby Hoffmann) has a different hairstyle in every scene, so it's no surprise that Grandma Rose doesn't recognize her. What is surprising is that Grandma Rose thinks Ali is someone named "Gershon."

Who's Gershon? Ali explains to Syd (played by Carrie Brownstein): "I think Gershon was Rose's brother, but it's all very murky—they don't tell me anything." All Ali knows is that Rose and Gershon left Berlin in the 1930s.

And then suddenly we're in Berlin in 1933, but only for a few moments: Young Rose is walking into some kind of institute, a transgender woman is smoking a cigarette in a book-lined room, there's an interaction between young Rose and the transgender woman, Gittel, but we can't really make sense of the conversation because we have no context for it.

Then we're back in the contemporary era—the whole season scrambles time this way—and Ali is camped out in the stacks of a library, reading about epigenetics. She looks up and says to Syd: "Oh my god, this shit is fascinating. Did you know there is such a thing as inherited trauma in your actual DNA?"

"No, I did not," says Syd, with perfect Carrie Brownstein flatness.

"They did this study on bunnies where they gave them electric shocks while they were smelling cherry blossoms, and the bunnies' babies, and their babies, the grandbabies—they were all afraid of cherry blossoms," Ali says.

Transparent is a character-driven show, full of subtleties and unlikable people and true Los Angeles weirdness, and the viewer is forgiven for assuming that epigenetics is just another of Ali's random quests. But it's not. The idea of trauma as a shared trait among family members, and passed down from generation to generation, even among family members who never meet each other, is the crux of season two.

This theme allows the show to offer its more subversive purpose: an impressionistic history lesson about gay culture. It's obvious that the show has lots to say about trans culture (its greatest achievement is launching characters into the mainstream unlike characters we've ever seen before, like Maura), and it has a truckload of lesbian culture (epitomized in season two by the Idyllwild Wimmin's Music Festival, a dyke summer camp for "women-born women" who have rules like yelling "Man on the land! Man on the land!" whenever male sanitation workers pull up to take their shit away), but there are vestiges of gay male history on the show, even though none of the principal characters are gay men.

But, again, it's impressionistic. You have to hit the history books to get all the references. Transparent creator Jill Soloway recently told an interviewer that she read Robert Beachy's book Gay Berlin while working on this season. Gay Berlin is a treasure trove of fascinating information: Did you know the term "homosexual" came from Berlin, and so did the idea of homosexuality as a fixed identity rather than a passing fancy? Did you know the first coming out in modern history happened in Berlin in 1867? Did you know the world's first gay-rights advocacy group, the Scientific-Humanitarian Committee, was founded in 1897 in Berlin by a medical doctor named Magnus Hirschfeld?

Hirschfeld housed the Scientific-Humanitarian Committee (along with research facilities, a library, a museum, medical exam rooms, etc.) in the Institute for Sexual Science, which is where the fictional Gittel is sitting smoking when Rose goes to visit her. The Institute for Sexual Science "offered medical and psychological counseling on a range of sexual issues to thousands of individuals, including heterosexual men and women, homosexuals, cross-dressers, and intersex individuals," Beachy writes in Gay Berlin. "The institute also represented the first attempt to establish 'sexology,' or sexual science, as a topic of legitimate academic study and research... With the X-ray, laboratory, and surgical facilities, the institute provided much more than counseling: Hirschfeld and his medical colleagues also pioneered some of the first primitive hormone treatments and sex-reassignment surgeries, effectively creating a nascent science of transsexuality."

Gay guys who think the trans movement has nothing to do with them may get their first inkling of how wrong they are by watching Transparent. The trans-rights movement and the gay-rights movement have always been linked through the work of Dr. Hirschfeld. They started in the same place, and originally they were thought to be essentially the same: Gay men in Berlin were thought to be "psychological hermaphrodites."

The Institute for Sexual Science was also a tourist attraction. The premises housed sexual artifacts, phalluses from around the world, photographs of men and women in drag alongside photos of them out of drag, and much more. You see some tourists being led through the place very briefly on Transparent. In 1929, the true-life tourists who stopped by included the novelist Christopher Isherwood and the poet W.H. Auden. "It begins with the Hirschfeld museum," Auden wrote in his diary after taking Isherwood. "We waited in an eighteenth century drawing room with elderly ladies and lovely young boys." According to Beachy, "Only later did Auden and Isherwood realize that those they encountered in the waiting room were not 'elderly ladies' but men in drag."

Isherwood and Auden would go on to become two of the most important gay writers of the 20th century, translating gayness as a fixed identity to Europe and the United States. Without Berlin, without Dr. Hirschfeld's institute, that may never have happened. (As Beachy writes: "Berlin's openness freed [Isherwood] not only to explore his homosexuality but ultimately to accept and embrace what he came to think of as a sexual orientation and identity. This was a freedom... [he] never felt in London.")

At the end of the second season of Transparent, Maura is still worried about revealing herself as a woman to her mother, Grandma Rose. Rose has not seen Maura since she was Mort. What Maura doesn't know—a brilliant, gut-churning twist—is that Rose's own brother, Gershon, transitioned to being Gittel shortly before the Nazis rose to power, with Rose's implicit support. Maura has no idea how ahead of the curve her mother is—has no idea of the traumas buried in that senile old brain. When Transparent shows the institute raided by the Nazis—based on real events—we see Gittel, frantic, kicking, on her way to certain death, being pulled away from a pile of books as Nazis set fire to it. But the season ends before any of those images are explained, and before we find out what happened to Gittel in the end.

There's a chance for season three to dig in a bit more, adding context and detail—and I hope Soloway goes for it, because the real history is fascinating (and until I read up on it, was entirely unknown to me). In his memoir Christopher and His Kind, Isherwood describes the raid on the Institute for Sexual Science. "They smashed the doors down and rushed into the building. They spent the morning pouring ink over carpets and manuscripts and loading their trucks with books from the Institute's library... It has been stated, since then, that some well-known members of the Nazi Party had previously been patients of Hirschfeld and that they were afraid that case histories revealing their homosexuality might be used against them." The raid and the book burning are documented in Gay Berlin, too, which emphasizes that Hirschfeld was doubly in danger—because not only was he gay, he was also a Jew. Luckily, Hirschfeld had already escaped to Paris. He watched the destruction of his institute—the starting place of gay culture and trans culture—"on a newsreel in a Parisian cinema."

It seems almost fitting that we should learn about it from a book, via a TV show.