Mourning the loss of the Kryptonians wiped out by Rogol Zaar, Supergirl decides to play detective and sets off into deep space to learn more about the would-be usurper. Superman and Supergirl, the last two Kryptonians on Earth, have had their beliefs shattered. With new revelations about their home planet--and the man who destroyed it--Supergirl builds a star cruiser using whatever tech she can scrounge, and after intel from Green Lantern, she blasts off into the cosmos with Rogol Zaar's deadly axe to solve the mystery--along with a traveling companion you won't believe!