In chapter four of the Bible, Cain kills Abel. It is the world's most famous murder. But the murder is silent about one key detail: the weapon Cain used to kill his brother. That weapon is still lost to history.In 1932, Mitchell Siegel was killed by gunshots. While mourning, his son dreamed of a bulletproof man and created Superman. The gun used in this unsolved murder has never been found. Until now. Today in Fort Lauderdale, a young man named Cal Harper encounters his long-missing father - who has been shot with the same gun that killed Siegel. But soon after their reunion, Cal and his dad are attacked by a killer tattooed with the ancient markings of Cain. What does Cain, history's greatest villain, has to do with Superman, the world's greatest hero? And what do two murders, committed thousands of years apart, have in common?