While Castiel was resolved to kill Jesse and prevent any evil the boy might commit in the🔑 future, the Winchesters believed his human half gave him the capacity for good. Instead of killing Jesse, they gave him🔑 the chance to disappear. After Jesse's introduction in Supernatural season 5, he was indeed never seen again.

Azazel orders the assassination🔑 of Sam's girlfriend Jessica Moore, who was a distraction. Her death prompts Sam to return to hunting. Demons cannot be🔑 killed by conventional means so the Winchesters track down the Colt a mystic gun capable of killing anything in "Dead🔑 Man's Blood".