ROME — The man approached Cardinal Angelo Comastri, prefect of the Fabric of St. Peter, with an odd proposition: Would the cardinal be interested in two documents written by the hand of Michelangelo, the Renaissance master?

Not only were the documents of historical significance, the man noted, they had also been reported stolen in 1997 from an archive in St. Peter’s Basilica, behind the high walls of the Vatican itself. Now the documents could be returned — for a price.

The cardinal refused. The Swiss Guards were notified. An investigation was begun.

“Clearly,” declared Il Messaggero, the Italian newspaper that broke the story on Sunday, “it was someone who had inside knowledge of the place.”

In fact, not much is clear. Cardinal Comastri declined to comment. Officials at the Vatican archive also demurred. And while Federico Lombardi, the Vatican spokesman, confirmed the basic facts of the case, he refrained from discussing the most intriguing details:

Who is the mystery man who approached the cardinal? Is he a former Vatican employee, as Il Messaggero reported? What should be deduced from the reported asking price of 100,000 euros (about $109,000)? Why did the documents suddenly emerge 18 years after disappearing?