“Old Stock: A Refugee Love Story” opens on a stage that is bare but for a shipping container, the kind that carries goods from borders to borders.

Unexpectedly, a trap door on its roof opens and Ben (Ben Caplan) pops up and breaks out in song.

Thus begins this exhilarating, klezmer-infused musical that is both joyful and sad, a reminder of old wounds and today’s headlines. It is innovative, perfectly cast, and made even more meaningful because it is at least partially based on playwright Hannah Moscovitch’s great-grandparents’ experiences.

When the shipping container opens completely, revealing the cast and musicians, Ben reappears in all his glory to continue his raspy-voiced singing:

“Who can deny your moral right to prosperity and order?

“You fell out of your mother on the correct side of the border.”

He is a sight: a wild-eyed cross between a chasidic rabbi in full flowing beard and a ringmaster in top hat and red-hued tails. He serves as both, periodically reminding us of appropriate Jewish tradition and mitzvot and also acting as narrator and jokester, keeping the play moving.

It begins at Halifax’s Pier 2, then the Canadian equivalent of Ellis Island. It is 1908, and Romanians Chaya (Mary Fay Coady) and Chaim (Chris Weatherstone), just off the boat, meet while waiting on a medical line, he because of a rash and she because of a cough.

It soon becomes clear that in addition to the physical luggage they carried with them, each also brought substantial emotional baggage. His family was slaughtered in a pogrom while the husband she still loves and reveres died of typhus as the family fled Romania for Russia.

Chaim is a youthful, naive 19-year-old who immediately falls for his new friend; Chaya is a 24-year-old widow. But more than age separates them. Chaim looks forward, optimistically expecting a bright future; Chaya is locked in the past, still in love with her dead husband, Yochay.

Both Coady and Weatherstone are extremely talented. In addition to their acting chores, they also sing and are part of the onstage band. She plays the violin, he the woodwinds. But more important, they bring an undeniable chemistry to their roles that likely will draw you in, making you wish (as I did) that despite obstacles they can make a life together.

They do, but it isn’t easy, because the past haunts even Chaim. Is it possible to find love or God after staring death in the face?

There are reminders everywhere, even in Canada: movie theaters reserved for gentiles and newspaper headlines that read: “Old Stock Canadians Soon To Be Overrun by Semitic Hordes.”

For Chaya especially there is the ghost of Yochay, which continues to haunt her, stepping between her and happiness. On their wedding night, young, naive Chaim wants reassurance of love from his bride, but instead Chaya tells him she can’t share his happiness: “All this joy you feel,” she explains. “I’ve felt it once before.”

It’s a challenging start to wedded bliss, further dampened when their first child develops a typhus-type rash.

At this point, even ringmaster Ben sees the musical going south. He turns to the audience and asks: “The laughs are turning into ‘why [the heck] did I come to see this depressing show?’ I hope you are not getting too depressed.”

When he next goes on to sing El Malei Rachamim, it’s hard not to feel dispirited, especially if you’ve vested so much in this couple’s happiness. (I did.)

But, spoiler alert, the prayer for the dead is a false flag, a misstep that made me feel manipulated, a misguided attempt to set me up for a happier ending to follow.

Another problem is an overuse of the “f” word, one I don’t need to hear over and over again. I know it’s prudish of me, but I feel an obligation to warn fellow prudes.

Still, I walked out buoyed by the jaunty songs by Ben Caplan; a creative set design, by Louise Adamson and Christian Barry with Andrew Cull, that makes excellent use of the small space, and spot-on lighting design, again by Adamson and Barry.

Barry, who co-created the show and is the playwright’s husband, also directed; he moves the well-cast players around with efficiency.

The real Chaim and Chaya lived long and I hope happy lives, with four children, eight grandchildren, and 16 great grandchildren. Last year, their 14th great great grandchild was born.

At the play’s end, Ben turns to the smiling actors and concludes with a fitting “mazel tov.”

“Old Stock: A Refugee Love Story” is at the 59E59 Theaters until April 22. Tickets, from $25 to $70, are available at www.59e59.org or from Ticket Central (212) 279-4200.