Father Christiaan Kappes, of Franklin, Ind., a priest for the Indianapolis Archdiocese, started a doctorate program in Athens, Greece, on behalf of the Vatican three years ago, WXIN-TV, Indianapolis, reported.
Three days ago, Kappes called his family to tell them he was trying to flee the country with his translator, Ioanna Lekakou, who was involved in a heated dispute over her family's inheritance.
"He told my dad on Monday, 'If you don't hear from me in 12 to 24 hours, I'm dead,'" said Nadia Charcap, Kappes' sister.
Earlier, Charcap said Kappes told her Lekakou's family "is out to get the money that she inherited and they are going to stop at nothing to hurt her in order to get this money. I asked him if he thought his life was in danger, if he thought anything was amiss and he was like, 'No they're just a bunch of thugs.'"
Virgil Kappes said he spoke to a priest in Greece who reportedly dropped off his son and Lekakou at the Athens airport.
"He said that he was going to buy plane tickets for both of them to go and leave the country," Virgil Kappes said.
"There's no reason to kill my son," Virgil Kappes said. "If they do they're heartless. They're cowards."
U.S. authorities are looking into the case, but Virgil Kappes said he is not confident they will be able to help his son in time.
"Somebody in the Greek government has got to step up," Virgil Kappes said. "Somebody in the Greek government has to go to bat. Somebody in the Greek government has to do their job right and get these people, and bring my son back if they can. If not, please let me get the body back."