AU set in the beginning of season 13. The boys did not make it to the cabin before Jack was born, so now they're one step behind and have no idea what happened. Cas and Lucifer have disappeared, a baby is nowhere to be found, and Crowley is alive and kicking. This is a terrible summary, full summary inside.
In 1999, Dean was killed in an accident, tilting Fate and the apocalypse on its ass. Ten years later, Sam makes a deal with the devil to give his family more time to put Lucifer on ice. In Gillette, WY X5-494 knows something is wrong. That out there where Ordinaries live, something important is happening, and he's supposed to be involved, helping the man with floppy brown hair...