The devil loves me

In an anonymous letter to Dr. Pry, an unknown murderer warns of his intention. He tells Pry that he's about to give him a murder to solve at his own doorstep, saying that it is high time someone combined a wedding and a funeral. He left the note in Pry's friend's pocket instead of the ring, "not because you can stop me, but merely to assure you that I am deadly serious." A bride, a groom, and a wedding feast are about to be interrupted by a clever killer. But will he be clever enough to get past Dr. Pry?