'Supernatural' season 12 spoilers & update: Winchesters reunite with Mom; Grim Reaper Billie returns to prey on hunters' souls

One would think that after killing Hitler, there is nothing that could possibly dampen Dean's (Jensen Ackles) days ever again. But the next episode of The CW's popular horror-fantasy series is about to flip the older Winchester's mood right back down on its head.

"Supernatural" season 12 episode 6 titled "Celebrating the Life of Asa Fox" will see a gathering of hunters to celebrate and mourn the life and death of a fellow hunter who went out in a tragic way. It seems to be a simple enough plot, except that it brings Mary (Samantha Smith) and her boys back in one place after she decided to leave and find her own way in the new world.

She also said some things that hit Dean hard, like how she preferred to have the memories of the younger Sam and Dean before indirectly expressing a reluctance to keep living her second life with the two fully grown sons she hardly knew.

There will surely be tension when the three of them meet again, but the gathering should also give them a chance to talk, especially since the episode will also bring back one of the Winchesters' most trusted allies, Sheriff Mills (Kim Rhodes). Mills has more than once given the boys straightforward and valuable advice, much like their late guardian Bobby (Jim Beaver).

Aside from the Winchesters' family drama, the episode will also feature the return of Grim Reaper Billie, who served both as an adversary and an ally for the Winchesters in the past. Which side will she be taking this time around? Will she help the brothers overcome the demon who crashes the gathering to pick off the hunters one by one? Or will she just be there waiting to reap some dead hunters' souls?

The trailer for the next episode shows the hunters in a dire situation after they find themselves trapped in a fully warded house in what is shaping up to be a cat-and-mouse game where everybody dies in the end.

How can the Winchester overcome a powerful adversary they can't even see? And how will the two most important women in their lives fare in the whole ordeal? Could they end up saving the day?

"Supernatural" season 12 episode 6 airs on Thursday, Nov. 17, at 9 p.m. EST on The CW.