A password will be e-mailed to you.

Somehow both old and familiar and also new and exciting, the World War II romance Dear Jack, Dear Louise, making its world premiere now at Arena Stage, is like a never-been-used antique that works like a charm.

Written by Ken Ludwig, directed by Jackie Maxwell, and going on now until December 29, this two-hander has lots and lots of heart, but a welcome amount of head, too. If my grandmother wasn’t 1,100 miles away, I’d try to bring her to see it, but it would be equally appropriate for a date night or holiday group outing.

Jack Ludwig (Jake Epstein), a doctor serving in the Army, and Louise Rabiner (Amelia Pedlow), an actress trying to make it on Broadway, live on opposite sides of the country in 1942, but their parents, who are old friends, think they should meet. So they strike up a correspondence and hit a garrulous rapport almost right away. He encourages her with her auditions; she commiserates over his hardass commanding officer. It isn’t long before we can feel these long-distance penpals fall in love as they read their own letters aloud. In one typical interchange, he noshes on some bagels she mailed him while she tells the funny story about what happened to the lox that was supposed to go with them.

The actors, each given half the stage, deliver almost all of their lines full front to the audience, but their epistolary dialogue is often cut together, so the show isn’t just a series of monologues. Who would have thought mail delivery was so fast in the 40’s! Louise tells Jack about meeting his family, to his chagrin. Jack tells Louise about treating the wounded coming in from the Pacific, to her sympathy. They make plans to meet, but circumstances and that darn ol’ war conspire to keep them apart.

Sound schmaltzy? Or worse, dusty? Two things save it from that: all the humor contained in Ludwig’s script, and the performances of the only two actors on stage, building chemistry without ever looking directly at each other.

Pedlow (so deliciously witty in Folger’s Love’s Labor’s Lost earlier this year) is as good with Louise’s dryer moments as she is with the emotional heavy lifting. Epstein (whose bio amusingly says he “survived playing Peter Parker/Spider-Man in Spider-Man: Turn Off the Dark” on Broadway) hides Jack’s vulnerability beneath an affable exterior. Both know a juicy role when they’ve landed it, and theatregoers should hope to see them again soon.

I don’t know what I expected from the set, but designer Beowulf Boritt’s ideas are better. The crinkled backdrop looks like paper fit for letter-writing, or perhaps well-used bed sheets, while oblong glass shapes dot the floor and ascend, suspended, up the back wall, like an Alexander Calder mobile viewed from underneath. The shapes look like thought bubbles, though they also symbolize a relationship built on stepping-stones.

Linda Cho selected the period costumes very carefully — not a lot of changes here — and with great attention to detail, from Jack’s gold-framed glasses to the impeccably straight seams in Louise’s stockings. Lights from Jason Lyons and sound by Lindsay Jones kick into high gear during war scenes, but nail the show’s quieter moments, too.

And throughout, the tone is one of warmth and understanding, treating the past not with the fetishism of nostalgia, but as a real place where real people lived. At one point Louise describes a particular family gathering as being “like a Norman Rockwell painting — if Norman Rockwell painted Jews.” He should have, of course. And the paintings should have looked like this.