The Amulet - The Midnight Eye Files, #1

It was supposed to be an easy case. Fast money, and a way to kill some time-something Derek Adams, a down-on-his-luck Glasgow private investigator, has way too much of. Recover a stolen family heirloom, and try to keep the relationship with his very beautiful-and very married-client, strictly professional. Easy. But the Johnson Amulet is no mere trinket...and Derek isn't the only person trying to find the priceless relic.
Before long he's up to his armpits in bodies, femme fatales... and tentacles. The stars have aligned... An ancient evil has awakened. To save the day, Derek must take some dark pathways, and not everyone is going to make it back out into the light.