From what we know so far about the possible spin-off, originally called "Supernatural: Tribes," like with the original series, the death of a loved one leads the main character into the world of monsters and hunting. It takes place in Chicago, with mafia-esque monster families running the city's underbelly. Lucien Laviscount plays the main character, Ennis, a police academy trainee, and it's his fiancée who is killed in the crossfire of the war. Stephen Martines plays his mentor and a Chicago cop who's on the payroll of one of the monster families.
Nathaniel Buzolic plays David, a shape-shifter who has been living as a human after giving up the monster life years ago. Danielle Savre will be playing Margo, the acting head of the leading shapeshifter family, and she feels threatened when her brother David returns to the family.
Sean Faris will be playing Julian, part of a wealthy werewolf family, and there's no love lost between his family and the shapeshifters'. Also in the werewolf family is Melissa Roxburgh's Violet, who hides her true nature because of her forbidden love for shapeshifter David.
Here's the official description of "Supernatural" season 9 episode 20, "Bloodlines," written by Andrew Dabb and directed by Robert Singer:
"SAM AND DEAN INVESTIGATE MONSTER FAMILIES IN CHICAGO — Sam (Jared Padalecki) and Dean (Jensen Ackles) investigate a case in Chicago, where they discover that various mafia-esque monster families are, unknown to humans, running the underbelly of Chicago. One is a family of shapeshifters run by Margo Lassiter (guest stars Danielle Savre), whose leadership is thrown into question when her brother David (guest star Nathaniel Buzolic) returns home. The other reigning family in town is made up of werewolves, lead by Julian Duval (guest star Sean Faris). While in Chicago, Sam and Dean meet Ennis (guest star Lucien Laviscount), a man with a personal vendetta against the monsters. The Winchesters warn Ennis about heading into the hunter lifestyle, but Ennis refuses to listen and starts down a dangerous path."
Will "Supernatural: Bloodlines" work? That remains to be seen, and they have to make a pretty strong case with this backdoor pilot since the CW has a pretty strong lineup right now. It has already renewed several shows for next season, and there is the "Arrow" spin-off to consider as well.
"Supernatural" season 9 airs Tuesdays at 9 p.m. on the CW. "Bloodlines" airs April 29. Do you think "Supernatural: Bloodlines" has what it takes to be its own series?