"First Blood" is the ninth episode and midseason premiere of the paranormal drama television series Supernatural's season 12, and the 250th overall.
Sam (Jared Padalecki) and Dean (Jensen Ackles) are taken to a government black site in the Rocky Mountain National Park, where they are locked in separate cells until they are willing to talk.
Sam and Dean are able to defeat the soldiers, then reunite with Castiel and Mary, who have found them with the help of Mick (Adam Fergus) and Arthur (David Haydn-Jones).
Mary chooses to sacrifice herself for her sons, but Castiel kills Billie instead, telling the horrified Winchesters that they are all too important for the world to lose.
Matt Fowler of IGN gave the episode a "good" 7.3 out of 10 and wrote in his verdict: "With 'First Blood,' the show sort of decided that Sam and Dean were finally in a bind that Cas, Mary, and Crowley couldn't touch.
"[3] Sean McKenna from TV Fanatic, gave a 3 star rating out of 5, stating: "I was expecting a lot more from this episode, especially for a midseason premiere.
I'm interested to see how things play out going forward with respect to killing Billie, but it felt like such a roundabout and unnecessary way to get there with the whole prison and then escape.