Georgia Skeehan is a rookie marshal with the New York City Fire Department but when an inferno in SoHo devours a small building and consumes fifty lives, she finds herself thrust into command of the investigation. She suspects the fire may have been started by HTA: a kitchen-sink concoction with the thermal power of rocket fuel. HTA fires, rare over the last decade, are so ferocious they can melt a building's steel and concrete framework in minutes. Soon, Georgia unearths the possibility that the blaze may be connected to three other unsolved New York fires, and to several eerie, scripture-laden letters from a madman who calls himself The Fourth Angel. But before Georgia can unravel the clues, she is shocked by the bizarre behavior of her partner, a man she trusts with her life, and by the seeming betrayal of another marshal, a man she has begun to trust with her heart. As Georgia battles for respect in the nearly all-male bastion of the FDNY, the Fourth Angel tightens his grip on his real quarry -- and plots an even more catastrophic and fiery finale.