A Roman Catholic priest faces federal charges for allegedly conspiring with a big-name Chicago mobster to recover a hidden antique violin.

In a two-count indictment announced Thursday by the U.S. Attorney’s Office in Chicago, a federal grand jury charges 62-year-old Eugene Klein, of Springfield, Missouri, an ex-federal prison chaplain who ministered to convicted Chicago mobster Frank Calabrese, Sr. Calabrese was a member of the Chicago outfit who was convicted as part of the so-called “Family Secrets” mob trial in 2007. He’s now serving a life prison sentence at a federal prison in Springfield, Missouri for racketeering, conspiracy and several murders.

The grand jury indictment alleges that Klein conspired to help the mobster recover an antique violin that Calabrese said he’d hidden in his summer house in Williams Bay, Wisconsin, near Lake Geneva. He said the instrument was made by legendary 18th century luthier Antonio Stradivari, and was “worth millions.” A document found by federal agents suggests the it was not a Stradivarius, however.

In March 2010, federal authorities seized some of Calabrese’s assets - including cash and jewels stashed in a secret compartment in his Oak Brook home - to contribute to more than $4.4 million in restitution payments Calabrese owes to the families of his seven murder victims. The indictment says agents also searched Calabrese’s Wisconsin home, but did not find the violin.

According to the indictment, Calabrese wanted to prevent the government from seizing the instrument, so he allegedly slipped Father Klein a note through the food slot in his cell door that had directions on how to find it. Klein and another person allegedly went to Wisconsin to recover the instrument - but it’s unclear if they ever did.

Prosecutors also say Klein carried messages from prison on behalf of Calabrese, even though Calabrese’s contact with the outside world is supposed to be tightly restricted.

Klein is charged with conspiracy and with trying to obstruct federal agents. If convicted, Klein could face up to ten years in prison. Attempts to reach him for comment were unsuccessful.

A spokesman for the Federal Bureau of Prisons said Klein is no longer a prison chaplain. But a spokeswoman for the Diocese of Springfield-Cape Girardeau, Missouri confirmed Klein is still an active priest, though he never had any official association with that diocese.