A blood-borne virus requires a blood-born cure, but can Ruby survive saving everyone else? The last few weeks sent Ruby Behl's world into even more of a tailspin than when the Tercera virus first broke out. Her boyfriend might be dead, her best friend isn't dead, and the man she knew as her father may have kidnapped her at birth. Worse, the virus suppressant suddenly stopped working, accelerating the deaths of thousands. Finding a cure just went from important to critical. Unfortunately, an essential piece of the puzzle fell into the hands of David Solomon, a zealous cult leader planning to massacre the remaining Marked-unless Ruby gives him what he wants: her blood, possibly all of it. Ruby must decide. Should she stay and help the Marked who rescued her or gamble on saving the entire world? As she grapples with the meaning of family and the value of a legacy, Ruby must decide who to trust-and who's worth saving in the first place.