Adam, the lost Winchester brother, is finally coming back to Supernatural - here's the character's tragic history and potential fate in Supernatural's final season. In Supernatural season 5, Lucifer had Sam Winchester lined up as his gated perfect vessel and, in need of a counter-measure, the forces of Heaven hope to pop the archangel Michael inside of Dean. With neither brother particularly fond of this plan, Heaven are left without a human body for Michael to wield. If only there was a third Winchester brother out there somewhere...
Cue Adam Milligan. Originally introduced in season 4's "Jump The Shark," Adam is the secret son of Sam and Dean's father, born around 7 years after the incident where Mary Winchester was killed by Azazel. Following a particularly troublesome hunt, Adam's mother is the unfortunate nurse tasked with stitching John Winchester back together. The duo hit it off and, sometime later, Adam is born. While John (unevenly) split his time between Adam and his other two sons, Sam and Dean have no idea Adam existed, and vice versa.
That was until a pair of ghouls seeking revenge on John tracked down Adam and his mother and brutally murdered them. Sam and Dean avenged their secret brother's death and gave him a hunter's funeral, but Adam's story didn't end on the pyre. With Dean putting up too much of a fight, Heaven still required a vessel for Michael to pilot in his fight against Lucifer and, since he possessed the Winchester bloodline, Adam was deemed "good enough" for the task, even though the angels initially only brought him back to act as bait for Dean.
The climactic showdown of Supernatural season 5 sees Lucifer (in Sam's body) face-off against Michael (in Adam's body) in a biblical archangel scrap that threatens the entire world. However, when Sam wrestles back enough control, he decides to jump headfirst into Lucifer's cage, sealing both himself and the devil inside for good. Adam and Michael are dragged along for the ride.
Strangely, Adam and his angelic occupant have yet to escape Lucifer's cage. Sam is quickly set free by Crowley, Hell's new King, and Lucifer eventually breaks free in Supernatural season 11 after convincing Castiel that only he has the power to defeat the Darkness. Adam and the prime universe's Michael are never seen again. The audience receives sporadic status updates on the third Winchester brother in later seasons, with both Lucifer and God confirming that Supernatural's only surviving archangel has gone mad from his years spent in the Cage.
It's certainly curious that the Winchesters don't make more of an effort to save their half-brother from his hellish fate. Given the lengths Sam and Dean go to in order to keep each other and the likes of Castiel, Mary and Jack safe - literally endangering the world on several occasions - it's odd that they don't make a more concerted attempt at bringing back Adam, especially after demonstrating their ability to access the Cage in season 11. Some viewers have always felt a twinge of hypocrisy when Sam and Dean preach the virtues of family ties, but largely seem to have forgotten their fellow sibling rotting in Hell through no fault of his own. Adam's lengthy absence may be at least partly due to the fact that Supernatural wasn't originally planned out beyond season 5, meaning there was no long-term story in place for Adam after being consigned to the Cage.
Fans aren't the only ones to call out Supernatural's abandonment of Adam, as even Sam Winchester actor, Jared Padalecki, has joked about the character's disappearance on his social media. As such, it's perhaps fitting that this loose plot thread should be addressed before Supernatural comes to an end. The most pressing question is whether Michael will still be inside Jake Abel's Adam when he returns. As the final archangel in the series, Supernatural can't just leave a deranged Michael hanging around, and the Winchesters' story would feel incomplete if they didn't make another attempt to rescue Adam. This suggests that the character will simply be lifted directly from the Cage onto Earth, most likely as part of God's mass resurrection in the season 14 finale.
Supernatural season 15 premieres October 10th on The CW.