The Singer and Dabb era covers Season 12 through Season 14 when Andrew Dabb became co-showrunner with Robert Singer following the departure of Jeremy Carver.
Sam is captured by Lady Toni Bevell, a rogue operative of the British Men of Letters.
Sam and Dean deal with the fall out of Jack's birth, Castiel's death, and Mary being lost in the Apocalypse World.
Sam and Castiel deal with Dean becoming Alternate Michael's vessel. Castiel helps a powerless Jack.