At the center of first-time author Paul Dionne’s new book is a 1,500-year-old edict that women can’t be priests anymore and the women who beg to differ.

Set in AD 495, the book is based on the epistle by Pope Gelasius. Dionne, the former Lewiston mayor and head of the state Workers’ Compensation Board, said he spent two years researching the era before he sat down to pen his historical fiction, “The Priestess and the Pope.”

Research and writing took nearly nine years. He celebrated its debut Friday night with an invitation-only signing at the Hilton Garden Inn in Auburn.

“It shows the role that women played in leadership roles, as martyrs, as prophets, and the very important role they played in the development of Christianity,” Dionne said. “There’s an awful lot of suspense, drama, mystery in the novel as we peel back the pages of time and go from the year 495 to the year 1.”

He winds the story around married priests Anna and Joshua, the young priest Maria, and Samuel, the aide Gelasius sends to southern Italy to relay the news. Dionne described his female leads as “strong, tough-minded women.”

“It rolls out as their struggle,” Dionne said. “A lot of Christians were martyred by Rome. These were not only men. Women were persecuted and executed and crucified and I wanted to bring that point out.”

He showed the latter with the book’s cover, a charcoal sketch of a crucified woman by Lewiston artist Luc Collette. Dionne said he reached out to the Maine College of Art to find Collette, wanting to keep ties to “The Priestess and the Pope” as local as possible.

Research for the book took him as far away as the Tip O’Neill Library at Boston College. Dionne said he found himself writing up to midnight and on weekends. Advice from a prospective agent had him pare down his original plan — all 2,000 years of Christianity in 1,000 pages — and, he said, that leaves him with a natural follow-up. Writing on book two started six months ago.

Dionne, 67, lives in Winthrop. When his state job ends next year, he plans to settle back in the Twin Cities and take up writing full time.

“Lewiston has always been my hometown,” he said. “That’s where I want to be.”

“The Priestess and the Pope” is self-published, available on Amazon.com ($14.95) and Dionne’s website. He said he hopes to get it into local bookstores and plans to hold signings this fall.

“It’s been a long process and it’s culminating in what I think is a very good read, a very good story, as well as sending a very powerful message,” he said. He added that deciding to ordain women again “is probably the best thing that could happen to the church.”

[email protected]