Evil in the Lake (Amen: American Exorcists, #1)

It has been here for decades... and it awakes every summer to claim new victims.

Paul is a young and forward-thinking university priest, so he can't imagine what the church bigwigs thought when sending him with the eccentric, volatile exorcist Father Conrad on a new investigation.
Their mission is to check out mysterious drownings in the quiet village of Elmwood, New York, which may involve unholy forces. But Paul doesn't even believe in the supernatural and he has his own demons to worry about.
As the investigation unfolds, however, Paul grows increasingly convinced something terrible is happening in Elmwood. More victims show up in terrifying circumstances and the town reveals its dark underbelly, with all signs pointing to an ominous presence lurking in the secluded lake.
Paul never expected he would have to fight for his life.
Now he might lose his soul.