<P> Azazel later uses his pact with Mary to enter their home in the pilot episode, and ultimately kills her . The second season episode "All Hell Breaks Loose, Part One" reveals that she had witnessed the demon secretly feeding his blood to Sam . John investigated the incident and learned of the existence of the supernatural . His desire to find and kill Azazel led him to become a hunter of supernatural creatures . He took his sons with him during his travels, but often left them alone in motels for long periods of time during his hunts, leaving Dean with instructions to "shoot first and ask questions later" while watching over Sam . </P> <P> As revealed in the fourth season episode "Jump the Shark," John slept with a woman he met while away on a hunt . Learning over a decade later that he had fathered her son Adam, John made occasional visits over the years to partake in father - son activities with him . He hid the truth from Adam to protect him, and never revealed to him the existence of Sam and Dean, nor vice versa . Meanwhile, John trained Sam and Dean to become hunters . However, Sam later left this life to start anew in college, leading to a fallout between John and his son . </P> <P> Twenty - two years after Mary's death, John disappears while on a hunt, forcing Sam and Dean to reunite in an unsuccessful attempt to find him . Sam returns to the life of a hunter after Azazel kills his girlfriend . John reluctantly chooses to avoid his sons throughout most of the season while he investigates something, eventually reuniting with them in the episode "Shadow ." However, the demonic Meg Masters attacks them and reveals that Azazel is after John . After escaping from Meg, the brothers split up from their father to keep him from the demons . When vampires murder his old mentor and steal the Colt--a mystical gun capable of killing anything--John teams up with Sam and Dean in "Dead Man's Blood" to retrieve it . Because demons cannot be killed by conventional means, they hope that the Colt will be effective against Azazel . In response, Meg begins killing the Winchesters' friends in "Salvation," and threatens to kill more unless they deliver the Colt . John is captured after trying to give her a fake gun, and reveals himself to be possessed by Azazel when the brothers come to his rescue in the first season finale "Devil's Trap ." However, he manages to resist the demon's control . Despite John's pleas for Sam to shoot him with the Colt, Sam cannot bring himself to do so and allows Azazel to escape . As the Winchesters flee in Dean's Impala, a demonically - possessed trucker crashes into them . </P> <P> In the second season premiere, "In My Time of Dying," Sam and John awake in the hospital with only minor injuries, but a dying Dean is comatose . John secretly summons Azazel, and seems to know what the demon's plans are . He then makes a deal to save Dean, giving up his life, soul, and the Colt . Before dying, John instructs Dean to kill Sam should he become evil . The fourth season episode "On the Head of a Pin" reveals that the demon Alastair tortured John in Hell for over a century, with John refusing the demon's offer to stop if he himself would torture someone else . His soul escapes from Hell in the second season finale "All Hell Breaks Loose, Part 2" when a gateway to Hell is opened . He saves Dean from Azazel, and distracts the demon by temporarily forcing him out of his host, long enough for Dean to kill Azazel with the Colt when he returns to his usual body . John then gives Sam and Dean a loving smile before becoming engulfed in a white light . However, the fifth season episode "Dark Side of the Moon" suggests that he might not be in Heaven . </P>

When do dean and sam find their dad