Nine years ago, researchers working at the Dutch national archives in The Hague were going through a box of declaration forms filed with the government in the late 1940s, seeking a work of art that had gone missing in the war, but had never been returned.

On one form, the claimant described a “large oil painting” in detail, including its title, “Le Repos,” its exact dimensions and the fact that it had been signed and dated by the artist in 1882. But what really caught the researchers’ attention was the name at the top of the form: Camille Pissarro, the 19th-century Impressionist.

“I was forced to sell the aforementioned piece to procure currency to survive,” wrote the claimant, Jaap van den Bergh. “Been in hiding for four years.”

Annelies Kool, a researcher with the archives, took the page and began a search that would not only locate the painting but would also illuminate the tragic story of two Jewish sisters whose parents could not keep them from perishing in a Nazi death camp.

Within days, Kool had located the work of art at a German museum. Within months, she had found a surviving van den Bergh heir, a daughter born after the war.

Now, after years of discussion, “Le Repos,” or “Girl Lying in the Grass,” is the subject of an unusual agreement in which the German museum, the Kunsthalle Bremen, will keep the painting but will help to publish a book that recounts the van den Bergh family’s history and losses.