Emma Winchester is the half sister of the infamous Sam and Dean and a Nefilim herself. At only 25 and despite her best judgement, the youngest sibling decides to go after Kelly Kline, Lucifer's baby incubator, without her big brothers. However, her intentions are far from malevolent. She believes Kelly's child can be good, a miracle if anything, and their only chance to get the devil under control again. As she ventures out into the unknown, working on her own for the first time in her short life, she gains Kelly's trust who proceeds to show her what her unborn child is capable of. On Kelly's side now, she makes Emma promise she will raise her baby as if it was her own and protect him with her life.
However, things get way out of hand when, in an imminent threat, the new born sends them both through a rift and into an alternative universe.