Dean discovers a birthmark on the baby Amara that is identical to the Mark of Cain, confirming her identity as The Darkness.
In this episode, Sam and Dean Winchester continue to deal with the immediate aftermath of releasing (Amara). The story splits between Sam's desperate attempt to find a cure for a mysterious "rabies-like" infection and Dean's encounter with the young Amara. Summary of Key Events [S11E2] Form and Void
The episode introduces the reaper Billie , who informs Sam that the old rules of "dying and coming back" are over. She warns him that the next time the Winchesters die, they will be thrown into "the Empty"—a place of nothingness from which there is no return. Dean discovers a birthmark on the baby Amara