Under the light of the full moon, a killer with a dark desire stalks the streets of New York City.
When a young woman is found eviscerated and laid out in a pentagram in Central Park, police quickly chalk it up to the work of a crackpot killer with a flair for the dramatic and a need for attention. But with the evidence not adding up and the body count rising, Detective Jack Hayes and his partner AJ realize that first impressions are often wrong.
Now, along with an unconventional occult expert, Jack and AJ have to do the impossible: find a man who kills seemingly without motive, before he goes down in history for committing the perfect crime.
Lose the first sentence and you've got the form for a hook down right.
The problem of course if you use this is that there is nothing to distinguish you from the 100 other novels about occult killers I've seen just today. You need to bring out what will make this novel a new and fresh take on an old trope.
Just as a side note, you mention the detective using two names, and the sidekick only one. Unless the sidekick has only one name, use both so that it's clear they are on equal footing.