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troperville

Sam and Dean receive a call on their dad's phone - it's Adam. Adam Milligan, John's other son, the one they didn't have a clue existed. His mother has gone missing and his town is suffering from a ghoulish mystery, who is stealing bodies from graves?

Tropes

Dead All Along
Decapitation Required: Blowing a ghoul's brains out also works.
Fantastic Slur: The ghouls take offense to being called ghouls.
Jumping the Shark: Lampshaded by the title; adding a new 'long lost family member' to a TV series is usually considered by its fans as one way a show has jumped the shark, but in this case, it isn't.
Long Lost Sibling
Not So Different
Parental Sexuality Squick
To Serve Man/You Are Who You Eat: The ghouls eat humans (usually ones that are already dead) and take on the form of the last person they ate.
Unusual Euphemism: "Maybe he slipped one past the goalie."
You Remind Me of X: Sam decides to be tough on Adam, who reminds him of himself when he was younger.