Can you solve the mystery of this Paris love letter?

CNN  — 

A lost love letter, a famous painting and a trail leading through the streets of Paris – do you have the answer to a romantic mystery that’s been perplexing a US filmmaker for two years?

Doug Block stumbled on the strange case of Betty and Henri while he and his wife were celebrating their wedding anniversary in Europe in late 2015.

“It all started in Paris,” the documentary maker recalls.

On the last day of their trip, the couple decided to go on a long stroll, savoring the fading autumnal daylight. Block fished out “Paris Walks,” the tattered, second-hand guidebook he’d stuffed in his suitcase at the last minute.

As he leafed through the pages, an envelope fell out, emblazoned with a single name: “Betty.”

“It just fluttered to the floor, almost like in slow motion,” Block tells CNN Travel.

The envelope was unsealed. Inside was a note card, adorned with a Monet painting: “Woman Seated under the Willows.” Written inside was a passionate declaration of affection.

“Will you look for me at the Musee D’Orsay?” wrote Henri, the mysterious author. “I will be there in soul and spirit, though not in body. It is there that you will find my love of Monet.”

Block turned to his wife in confusion. Who was Betty? Who was Henri? And how did this letter end up in his guidebook?

Little did he know the letter would mark the beginning of an globe-spanning quest, an international labor of love celebrating Paris and the enduring power of romance.

A serendipitous discovery

Doug Block found a mysterious love letter referencing the Musée d'Orsay.

Block and his wife traveled to Paris in November 2015. They spent their days wandering the wide boulevards, strolling the Seine and admiring the Impressionist greats in the Musée d’Orsay.

On their second evening in Paris, a Friday on November 13, the city was rocked by a series of deadly attacks in which 130 people died.

“I remember I had been thinking, ‘Oh my God, Paris, the city of love and romance is now going to be associated with terrorism,’ ” says Block.

Unearthing the love letter seemed like a sign from fate – a serendipitous reminder of romance in a moment of heartbreak.

“The love letter hit home,” he says. “The timing of it, in terms of everything that Paris was going through and the whole response internationally to the terrorist attack.