Threats multiply in the Reign of X! As Cable and his allies get closer to the secret of the missing mutant baby, a fateful reckoning draws ever closer! The origin of the Children of the Atom is revealed - but who really are these junior X-Men behind their masks? Meanwhile, an invisible threat is loose on the island of Krakoa - unseen, unheard, undetectable by any...except Excalibur. Elsewhere, one of the deadliest enemies in the history - and future - of the X-Men comes online. And when Mister Sinister goes missing, can the Hellions unravel the mystery? Collecting CABLE (2020) #10, CHILDREN OF THE ATOM #3, EXCALIBUR (2019) #20, X-MEN (2019) #20 and HELLIONS #9-10.