The Summoning Fire by David Michael
Reese Howard used to be an enforcer for the half-devil crime boss known as the Old Man. Now she has nothing. Her lover and partner, Sam, is dead. The Old Man betrayed them. He killed Sam in front of Reese, a blood sacrifice to fuel his latest power play in Hell on Earth. Reese hopes the Old Man made a mistake, leaving her alive. But she has no doubt he’s waiting for her, beside The Summoning Fire.