LITTLETON — They were teenagers, just kids really, fresh out of high school and eager to explore beyond the horizons of their hometowns. She wanted to learn German. He wanted to learn English.

And so, a relationship was born. Their letters to each other, yellowed now with the age of nearly eight decades, are a time capsule that chronicles events big and small, life-changing and life-affirming: assassinations and moonshots, love and marriage, the indignities that come with old age.

“The teacher asked if anybody wanted a pen pal,’’ Grace Lindquist said this week, the correspondence of a lifetime spilled across her dining room table here. “And apparently, Heinz was asked the same thing.’’

It was 1937 and their first letters to each others were, quite naturally, formal and stilted. Who are you? Where were you born? What do you do? Talk about your family.

And then, almost before their trans-Atlantic correspondence moved into maturity, a world war broke out. Their countries became sworn enemies in bloody conflict. And so, Grace believed, that was that.

Then, in June 1946, Heinz Borowski broke a years-long silence, writing a letter from Berlin that began: “Dear Grace!

“You will be astonished to hear from me. I didn’t know, do you remember me? A long time has gone, when I get your last letter. It was in 1938. From that time till now we had verry hard times.’’

Heinz was a member of the Wehrmacht, Hitler’s regular fighting force that suffered massive casualties in the war. More than 5 millionWehrmacht soldiers died. Many Germans regard the Wehrmacht as honorable soldiers who only fought the enemy, although there is evidence those soldiers, too, participated in the war crimes.

In any event, by the time Heinz and Grace resumed their long-distance relationship, he was recuperating from war wounds. He was shot twice in his left arm. Berlin lay in ruins, as did his plans to attend college.

“Now, I have told you something from me and I don’t ask you what you did all the time from 1938 to now,’’ he wrote. “Certainly, you are married. You had been 27 years on 12 June. Therefore I congratulate you.’’

Yes, Grace Van Dam was now Grace Lindquist, a native of Rochester, N.Y., who grew up in the Depression and set course on a life as a secretary, a music teacher, and a social justice activist — the kind of person who, if you were lucky enough to find beside you at a dinner party, would make you forget about others at the table.

Young Heinz needed help. Food, soap, clothing. Send me your hand-me-downs, he asked. “It is painful for me to say,’’ he wrote to her in late 1947. “Through the war, I lost all my clothes.’’ So she sent him some. And the old pen pals began to forge something deeper: friendship.

“Why continue?’’ she said, repeating my question. “It was an appeal for help.’’

That help was met with a gratitude never forgotten. “The wretchedness in our native country is so great that each gift — is it even so little — is a great help. You have proved a great joy,’’ he wrote.

Their letters are marbled with the mundane and the monumental. The Marshall Plan’s reconstruction. The division of Berlin. News that Heinz, on his way to law school by then, had met a 23-year-old railway worker named Ursula. “The wedding is Easter!’’ he wrote.

“The chances in this profession are very bad because there are nearly no lawyers in the Eastern zone of German,’’ Heinz wrote from Berlin in 1950. “The greatest part of them had fled or are sitting in concentration camp.’’

There are mentions of cold winters. Heinz congratulates Grace on her new kitten. When her son turned 5, he sent a card, signing it — to her delight — “Uncle Heinz.’’

Heinz was there on June 26, 1963, when President Kennedy delivered his famous “Ich bin ein Berliner’’ speech. Remarkably, in a letter dated Nov. 22, 1963, he wrote of that visit, apparently just hours before Kennedy was murdered in Dallas.

“I send you a simple black and white picture of the Kennedy visit in Berlin,’’ he wrote in the letter. “You cannot imagine how much enthusiasm your president was welcomed here.’’

In the summer of 1970, Grace and her husband flew to Berlin to meet Heinz and his wife. Heinz, formally dressed, carried a dozen roses and a German-to-English dictionary.

“We were all crying,’’ Grace, now 97, told me this week. “There was a warmth. You could feel it. It was really a high point in my life. I’m very emotional about it.’’

Grace Lindquist is a remarkable woman. She marched for civil rights in Alabama. She protested the Vietnam War, picketing at the Pentagon. She taught guitar and piano to 200 kids. She’s writing her memoirs. I’d love to read them.

“The reason I kept going was that there was so much anti-German and anti-Japanese sentiment,’’ she said. “I felt I didn’t want to be a part of that prejudice. Plus, I was impressed by his intelligence. That kept me going, I think.’’

She’s going still. Her correspondence with 98-year-old Heinz, who ultimately became a judge, has dwindled. But the two now speak by phone most Sundays.

“He’s about my dearest friend,’’ she said, her eyes glistening. “My dearest living friend.’’

For all the words they’ve exchanged over the years, there’s one thing she’s never asked him: Did you keep my letters?

She’d love to know the answer. I think I know it.

Thomas Farragher is a Globe columnist. He can be reached at thomas.farragher@globe.com.