Demolition was halted to figure out what the painting was and how it came to be in what was about to be a shop. Seeing the aristocrats on horseback and the mosque in the picture, Mr. Bolen said, visions of Crusaders and Knights Templar began to dance in his head. “I think maybe I have seen too many movies,” he said.

A Whodunit

In the game of six degrees of separation, this was a good one: Mr. Bolen’s mother-in-law, Annette de la Renta, had cousins (via her mother, Jane Engelhard) who had married into the de La Rochefoucauld family, storied members of the French aristocracy. One of those family members happened to live across the street from the new de la Renta boutique.

So when the painting was found, and it became clear Mr. Bolen would have to talk to the building’s owners, whom he had never met (the lease had been negotiated through a broker), his relative was able to make the introductions. Another de La Rochefoucauld, who happened to work at the Louvre, got a recommendation for an art historian: Stephane Pinta of the Cabinet Turquin, an expert in old-master paintings.

Mr. Pinta determined that the painting was an oil on canvas created in 1674 by Arnould de Vuez, a painter who worked with Charles Le Brun, the first painter to Louis XIV and designer of interiors of the Château de Versailles. After working with Le Brun, de Vuez, who was known for getting involved in duels of honor, was forced to flee France and ended up in Constantinople.

Mr. Pinta traced the painting to a plate that was reproduced in the 1900 book “Odyssey of an Ambassador: The Travels of the Marquis de Nointel, 1670-1680” by Albert Vandal, which told the story of the travels of Charles-Marie-François Olier, Marquis de Nointel et d’Angervilliers, Louis XIV’s ambassador to the Ottoman Court. On Page 129, there is a rotogravure of an artwork depicting the Marquis de Nointel arriving in Jerusalem with great pomp and circumstance — the painting on the wall.

But how it ended up glued to that wall, no one knew, nor why it was covered up. There was speculation that maybe it happened during World War II, given the setting. It could be “a fog-of-war issue,” Mr. Bolen said.