Mark just watched his partner and best friend of 10 years torn limb from limb by the kind of unholy horror that leaves most people gibbering in terror. Only a combination of luck and skill kept Mark from sharing his partner's fate and being killed by an abomination that by rights shouldn't exist in this day and age.
When asked, Mark tells people he works recovering stolen artifacts, and that's true. However he's also a member of a very old and secret organization that protects the world from devils and demons summoned here to do evil. A foot soldier on the front lines of the eternal war between Heaven and Hell, things had been favoring the side of Heaven for some time now. Until today that is, when someone discovered how to summon a devil that no one had seen since WWII.
Never popular with his boss, Mark finds himself sidelined as he tries to discover just what happened. Upset with being taken off the case, Mark does discover one thing rather quickly: whoever is behind this is now after him, and if he's not careful he'll be joining his partner sooner, rather than later.