Ghost Squad 10 - Trick or Death - A Rest in Peace Crime Story, #10

It was a quiet morning in the Cold Case office, as Detective Russ Baker sat contemplating his life. Then his ghost partner, Wes, materialized and had an unbelievable tale of a zombie apocalypse if the Ghost Squad couldn't find the killers of three Satan worshipping priests. Halloween would be the night for the doom of the world if they failed. They have to reopen a ten year old case and track down anyone involved in the murders to find who actually shot the men and stop the curse from the demons who appeared that fateful day.
With only days left, they hunt for the killers to get them to confess. This is the tenth book of the Ghost Squad series and it's a novella, shorter than a novel but longer than a short story