Bring Him Back, Jack

Once every century, a shadow walker is born. Ivan Charna is that shadow walker, and he and his sister Raina are on the run from wizards who want to sacrifice their blood in some crazy rite. They never stay long in one place, and they do their best not to stand out. When Raina loses a bet, Ivan is forced to work off her debt, and they have to stay put. As long as no wizard figures out what they are, Ivan doesn't mind all that much since he gets to work with his favorite vampire. Malik lives in a cell in a basement. He's never allowed to go anywhere without chains around his wrists and ankles, and there is a stake hovering over his heart at all times. Master can trigger the stake with a push of a button. He doesn't even have to be in the same room to do it. Malik dreams of a different life, a life with Ivan, but he's a vampire, and vampires have to do what their masters tell them.  Ivan only has to steal one last diamond, then the debt is paid, and he and Raina can leave town. It should be easy, but when Remington Redwood, the man Raina owes money, insists on having Malik shadow his every step, it complicates things. Malik might dream about making Ivan his, but getting him away from Master alive has to be enough. Ivan knows it's a stupid risk to take, but if he's stealing a diamond, what's to say he can't steal a giant vampire too?