CAMBRIDGE — For decades, Brian Cutler’s family had no idea who was leaving flowers on his uncle’s grave at Cambridge Cemetery each Memorial Day weekend.

As part of an annual tradition, the family would arrive at the cemetery the day before the holiday to pay respects to his uncle and father, who had both served during World War II. And each time they walked up to the flat marker bearing 2nd Lieutenant Burton W. Cutler’s name, there stood a collection of purple flowers, set in a small wooden planter.

“We had always come up here on a Sunday — Sunday was always our day,’’ said Cutler, 48, as he stood near his uncle’s gravestone, recalling the mystery that has since been solved. “And the flowers were always there in advance.’’

It wasn’t until he was in his 20s that Cutler, overcome with curiosity, finally put an end to the enigma that for so long had captivated his relatives. What he unraveled, it turned out, was a tale of love and loss.

In 1996, Cutler was lying in bed at his home in Gloucester when he decided to drive down to Cambridge Cemetery and leave a note imploring the person who had been leaving the flowers for so many years to call him.

When Cutler returned the following day with his family on their regular Memorial Day weekend trek, he discovered the person had replied. There on the note that he had left was a woman’s name, Rita, along with a phone number, address, and — “like clockwork,’’ he said — the purple flowers that for so long had been shrouded in secrecy.

Cutler said he immediately ran off to locate a pay phone and called the number the woman had left.

During their brief exchange, Rita, he said, explained that she had been married for a short time to his uncle until 1943, when he was killed in the line of duty.

“The myth was no longer a myth,’’ he said. “It was real.’’

Taken aback, Cutlersaid, he arranged to meet with Rita at her home in Cambridge a week later, along with his mother and sister.

As Cutler remembers it, the sun was up when the family arrived, and dark by the time they had left.

During those hours, he said, Rita detailed the monthslong love affair she had with Cutler’s uncle, before it ended in tragedy.

Rita told the family that she had been engaged to another man who had been deployed overseas with the Navy during the war. But then she met Burton Cutler, and the young couple fell deeply in love, almost unexepectedly.

Emmy Cutler, Brian’s mother, said Rita wrote a “Dear John’’ letter to the man she had planned to marry. In the note, she included herengagement ring.

Soon after, Rita married Burton. After they were together just a few months, he was sent overseas with the ­Army Air Force. He was killed when his plane was shot down over Sicily, according to his family.

When the war ended and the soldiers returned home, Rita ended up marrying the man whom she had cast aside to be with Burton, Emmy Cutler said.

“It was tough for him to accept what had happened, after his girlfriend had jilted him for another man,’’ she said.

“So out of respect, she promised herself she would never mention the name of her short-lived romance.’’

“They thought their lives would take different paths,’’ Brian Cutler added. “Fate intervened, and she ended up back with him.’’

The Globe could not independently confirm the details of Rita’s love story. But the Cutlers, who lost contact with Rita before she died, said the woman responsible for placing flowers at the grave provided them with a box of items that had belonged to Burton, including photographs of the couple together on the beach in Gloucester.

“It still gives us chills,’’ said Brian Cutler, looking back on the series of events that unveiled a piece of family history that many of them were unaware of. “It was mind-blowing.’’

Decades after the mystery was solved, the Cutlers continue the tradition of visiting the cemetery ahead of the emotional holiday in remembrance of those who have served their country.

On Sunday afternoon, as the sun gave way to heavy clouds, Brian Cutler’s 13-year-old son, David, leaned forward and used a spade to clear away the grass that had moved in around the gray slab marking his great-uncle’s burial site.

And there, beneath an American flag, the family placed a pot of flowers.

This time, they were orange and yellow.

Steve Annear can be reached at steve.annear@globe.com. Follow him on Twitter @steveannear.