A lot of the story in the novel takes place in St. Clement's Episcopal Church. In the South, that was the denomination of prestige and of the leading social class. That was a carryover from colonial days when the Anglicans dominated. These days the denomination is more progressive, but there still is the lingering aura of prestige in some parishes.
In a decently-run parish, the clergy serving is called the rector. An interim rector is not intended to be there permanently. He or she comes for a fixed period or to fulfill a task. Perhaps there has been a long-tenured rector, and a new face is needed. Or maybe there has been some upheaval, and someone has to clean up a mess.
Enter Father Michael Bertoni, retired US Army chaplain. He is from Philadelphia, a member of another diocese, and comes to St. Clement's after Father Jonathan Stallworth protested changes in the denomination. Eventually, he joined a non-canonical Orthodox group and set up a chapel in town.
Interims are not there to be popular, but to make some hard decisions and to clean things up. Some members of St. Clement's love him, others, like Eustacia Botley, do not.
I have been an interim pastor in the Evangelical Lutheran Church in America, usually in less tumultuous situations. Since we are partners with the Episcopal Church, I was going to be an interim rector in Pennsylvania, but later that week I learned I was being deployed to Germany.
Fr. Bertoni's sermons in the novel set the tone for what St. Clement's and its members need to be. What happens in the holiday services shows the tensions and the joys in the community. The main characters find out a lot about themselves there, and that carries over to their everyday lives.