Theirs was a forbidden love, yet it persisted despite relentless efforts to eradicate all communication — even longing glances — between them.

It began late last year, in early December. The first to speak was the blue mailbox: “(Heart) U,” she said, tenderly gazing over at the green mailbox leaning toward her.

“(Heart) U Too,” he responded, fondly returning her glance.

As people walked past the northeast corner of East 12th Avenue and Lafayette Street, they noticed the heavy-metal lovers. Soon, photographs of the pair showed up on Unseen Denver, a social-media blog that archives images and words which affectionately document the ways Denver residents celebrate their city.

“Two pictures of the mailboxes showed up in my inbox within hours of each other on Dec. 12,” says Rick Ramos, who manages UnseenDenver.com.

Among the photographers: recent Denver transplant Jasmine Cann, who wrote about the enamored mailboxes on the BeatOfTravel.com blog she writes with her husband, Derek.

“Then one day last summer, I went out for a run, and the mailboxes were painted over,” she said. “When I got home, I told Derek. I was bummed out, and Derek was bummed out. But then a few days later, we were out walking the dog, and they were back.”

On Aug. 15, the messages were “Missed U” and “Missed U Too.” Before long, more blue and green paint silenced the conversation.

Then the faces were back. “They Can Never (Heart)” “Tear Us Apart (Heart)” the two announced. People taped congratulatory notes to the mailboxes. One read, “Graffiti is in the eye of the beholder (I like).”

But someone didn’t like. Big circles of white spray paint covered the faces. A few hours later, two green peace signs appeared atop the circles.

“They’re kind of like a romantic Zorro,” Cann says. “It really is intriguing. Graffiti is graffiti but this is something different. There’s a sweetness to it.”

What will the next chapter be? Only one thing is for sure, says Chris Stroup, station manager for the Capitol Hill U.S. Postal Service office, whose territory includes the clandestine love affair.

“For us, it’s graffiti, and if we see it, we’re going to call the maintenance guys to come paint over it,” he said.

Photos courtesy of unseendenver.com and beatoftravel.com.

Claire Martin: 303-954-1477 or cmartin@denverpost.com