As Michael Rosen’s poem insists, fascism doesn’t come in fancy dress. It doesn’t show up in jackboots and swastika tattoos. It makes itself presentable: puts on a suit, borrows a tie. It comes kissing babies and handing out hats. It goes by new names: alt-this, freedom-that.

In Roland Schimmelpfennig’s play Winter Solstice, it arrives in the form of a kindly old man one Christmas Eve. Rudolph Mayer rings the doorbell of a smart family home and finds himself invited in. His hosts are well-to-do liberals: a social historian and his artist wife, university-educated, cultured and polite. Their bookshelves are lined with studies of the Third Reich. You’d think they’d be inoculated against nazism, primed not only to identify it, but to denounce its logic and resist its rhetoric. And yet, they aren’t and they can’t. Rudolph Mayer runs rings around them.

“How is it possible that someone could turn up and be such a blatant Nazi and yet, one by one, everyone waves it through?” asks Ramin Gray, who is directing the play at the Orange Tree, Richmond, in a co-production with his Actors Touring Company. “I mean, it’s totally obvious from the get-go who this man is. It’s not like there’s some big reveal … It’s so obvious, and yet no one says a thing.”

Facebook Twitter Pinterest Zombie fascism … Nicholas Le Prevost, who plays Rudolph Mayer in Winter Solstice. Photograph: Stephen Cummiskey

Schimmelpfennig – his name translates as “mouldy coin” – is one of Germany’s most prolific playwrights. At 49, he’s had more than 30 plays produced at home, many of which have been staged in translation elsewhere. Britain has seen only a select few, but those that have played here have been both sharp and idiosyncratic. Push Up, at the Royal Court in 2002, presented a corporate culture where cut-throat employees oust their cut-throat bosses to get to the top. Arabian Night (Soho theatre, 2002) unpicked the psyche of modern, multicultural cities, where myths intermingle and identities entangle. The Golden Dragon (Traverse, 2011), set in a Chinese takeaway, continued the theme.

Still Winter Solstice might be his most pertinent play yet. It is a portrait of zombie fascism, nazism back from the dead, and yet, on its German premiere two years ago, critics tended not to take it entirely seriously – much to Schimmelpfennig’s alarm. “They felt it was more a portrayal of a neurotic, well-living leftwing intellectual,” he recalls. “My focus was always on the method of the ‘fascist’ seduction.”

That’s almost exactly the problem the play diagnoses. Seeing Winter Solstice as a satire essentially rejects the possibility, let alone the reality, of fascism’s return – much as Schimmelpfennig’s historian does. They treated Rudolph as a literary cipher, not a credible threat. “The anti-European success of the AfD [Germany’s far-right party, currently polling at 15%] seemed to many unthinkable, just as Brexit and Donald Trump were unthinkable,” Schimmelpfennig explains. “Things have changed a lot.”

The playwright has long insisted otherwise. For him, it was enough that rightwing populism had gained a foothold: “Its presence was already more than clear. It just didn’t have a face.” Winter Solstice was a warning against allowing its advance. “The play was triggered by the nightmare that this way of thinking would become salonfähig – meaning that it would successfully enter into the living rooms and dining tables of polite society.”

Facebook Twitter Pinterest David Tennant and Jacqueline Cinque in Schimmelpfennig’s Push Up at the Royal Court Upstairs, 2002. Photograph: Tristram Kenton/The Guardian

Once it’s allowed in, the play argues, such thinking takes hold. Allow it to become acceptable and it will be accepted. One by one, Albert’s family come round to Rudolph’s ideas.

Schimmelpfennig’s point is that they’re nothing if not persuasive. “He talks about unity and the need to come together,” explains Gray, “but he doesn’t say for what. He says the world is fractured and falling apart.” Most of all, Rudolph mixes art and culture with nationalism and xenophobia. “It’s not new,” Schimmelpfennig points out. “It works every time – and it’s horrible.”

However, it only works if left unchecked. Though not the satire it was taken for, Winter Solstice warns against the weakness of the liberal position. Albert can’t bring himself to stand up to Rudolph. He’s too polite to challenge him; too forbearing to kick back. To do so, says Gray, “you have to start labelling people. You have to deny them the right to define themselves as they wish, which isn’t at all liberal.”

“How do you tolerate intolerance?” he wonders. “Sometimes you have to step up and say, ‘No, I’m sorry …’” Gray stops himself and laughs. “You see. I said, ‘I’m sorry.’ It has to be: ‘No. Fuck off.’ Those are the muscles that are weak.”

Facebook Twitter Pinterest The Golden Dragon by Ronald Schimmelpfennig at the Traverse, Edinburgh, in 2011. Photograph: Murdo MacLeod/The Guardian

Gray likens theatre to a gym. He sees it as an art form that activates audiences. It’s easy to see why he admires Schimmelpfennig. The German makes his audiences work. Having started out in journalism, he came to theatre late: “I wasn’t able to capture the truth, so maybe that’s why I started to invent my own stories.”

Those stories are often self-aware. They stress their status as stories, and Gray believes Schimmelpfennig’s stints as a dramaturg, first at the Munich Kammerspiele, then the Schaubühne, are reflected in his writing. “He knows plays inside out; how rehearsal rooms work, how actors work, how processes work. Some of his writing feels just like being in a rehearsal room.”

There is, in other words, a sense of discovery, as if actors are finding their footing as they go. They seem to argue with one another, disputing one another’s accounts and pulling a story this way and that. Winter Solstice splices dialogue with narration; either fact, testimony or a film script spoken aloud. Idomeneus, seen at the Gate two years ago, had a chorus contradict one another. The myth mutated as it was told.

It’s Brechtian, yes, but more than that, it opens up narratives into multiplicity and uncertainty. It turns one play into many. “When people gather to follow a play, they share a story,” Schimmelpfennig says. “In a way, theatre opens up a dialogue.” Having recently started writing novels, he compares “rooms full of spectators” with a reader, singular and alone.

Out of ambiguity, his plays demand attention and interpretation. They’re laced with magic realism: teeth that travel the world, indoor deserts. Time often loops back on itself. He makes us watch things again and again, from one perspective then another. As in Winter Solstice, the past seeps into the present.

“Time is our master,” Schimmelpfennig stresses. “So playing with time is like a luxury and an act of anarchy. Theatre bends time all the time, theatre dominates time. It’s a human privilege to be able to do so. It’s a moment of ultimate freedom – till the curtain falls and everybody rushes to the underground.”