After his angels capture one of Metatron's followers, Ezra (guest star Gordon Michael Woolvett), Castiel calls in Sam and Dean to interrogate him. Sam and Dean are able to trick Ezra into revealing that Metatron has a secret portal into Heaven for his followers and is amassing an elite ground force for an unknown reason. Before they can get more out of him, Ezra is assassinated by a spy in Castiel's ranks. In response, Castiel meets with Gadreel (guest star Tahmoh Penikett) to discuss him becoming a spy for his faction. Castiel is ambushed at the meeting, but Gadreel insists he had nothing to do with it. Castiel attempts to convince Gadreel that he is fighting for the wrong side and that he should become Castiel's spy and leaves him with the offer. At the same time, Abaddon (guest star Alaina Huffman) travels back in time to 1723 and kidnaps Crowley's son Gavin to use as leverage against him. Crowley agrees to help Abaddon kill the Winchesters and leads them to where he has hidden the First Blade, but secretly warns Dean of the trap. After sending Sam on a wild goose chase, Dean confronts Abaddon alone. Despite initially being no match for her, the Mark of Cain eventually grants Dean immunity to her powers and telekinesis, allowing Dean to gain the upper hand and finally kill Abaddon. However, the rage from the Mark causes him to mutilate Abaddon's corpse until Sam stops him. The Winchesters allow Crowley to live, but he teleports Gavin away so he won't be returned to his own time to die. In the aftermath, Dean refuses to be parted from the First Blade, claiming that it grants him a calmness and strength despite Sam's worries of what it's doing to him.