After last night’s major reveals about the Winchester family legacy, Supernatural executive producer Robert Singer previews what comes next for Sam and Dean. Major spoilers ahead.

In “As Time Goes By,” Sam and Dean’s paternal grandfather, Henry, traveled through time with one of the most powerful demons in existence on his heels.

He revealed that he was part of a group known as the Men of Letters, keepers of information about the supernatural who passed it on to elite hunters.

Sam and Dean, it turns out, are legacies of this group. Before their deaths, the final Men of Letters survivor and Henry passed on the location and key to a Men of Letters bunker.

So what comes next for the brothers, who are in the middle of a quest to shut the gates of Hell permanently? TVOvermind has a spoiler-filled preview from Singer.

The brothers will visit the bunker in the next episode, and “it’ll become kind of a home base for the boys…for quite some time. Singer goes on to describe the bunker set as “really stunning.” He adds that “[i]t’s a very expensive set and we’re going to be using it [a lot].”

Singer equates the information contained in the bunker with multiplying John’s hunter’s journal “times 100” because “it’s got every source of information that would be interesting to the boys.” And “when they get in there, Sam is totally immersed in the place and Dean is just happy to have his own room,” Singer laughs.

Because of the sensitive information the bunker contains, Sam and Dean will “go to great pains to keep [the bunker] hidden. It’s also kind of impenetrable,” Singer previews. Like Bobby’s house and Rufus’ cabin, it will become “a place where they can decompress, have their bromance.” The bunker set gives them “lots of room to move around” and includes “lots of really cool things.”

The bunker will be more than a font of information and a home base, though. It “plays into the tablet business,” Singer explains. “If, for instance, Crowley got his hands on the Angel Tablet and could somehow decipher it it would be kind of a bad thing.”

If “[t]he information that is contained in this Men of Letters bunker” were to fall “into the wrong hands,” it “would be quite a powerful weapon against the boys. So it has to remain a secret and guarded closely.”

As for who might find out about it, Singer says, “I think it’s on a need to know basis. I don’t think you’re going to have a hunter convention in there. It’s not their style.” However, Singer “would be surprised if Garth didn’t show up and probably break an expensive globe.”

He adds, “As we go down the life for the rest of this year and hopefully next year, dramatic turns will take place because this is an important place.”

Burying their grandfather and finding the bunker will particularly affect Sam, according to Singer. “When we get [deeper] into this whole idea of closing the Gates of Hell, that becomes a real raison d’être for Sam,” he says. “It’s really revenge motivated,” as demons killed their parents, friends, and Sam’s girlfriend, Jessica.

Because of that history, “I think Sam would see that there’s a certain amount of closure if they could pull this off,” Singer explains. “I think still he, in the back of mind thinks there’s a normal life out there for him,” though it obviously didn’t pan out with Amelia. “In a way, Dean’s on board with that. He’d like to see [Sam] happy, but they have this one thing to do.”

Of course, this being television, “they’ll have something else to do down the line,” but “I think it’s actually a good separation of character for the two of them that one has one set of dreams and actually allows himself to dream while the other is much more fatalistic and sort of accepts that.”

The brothers have switched between these roles over the course of the series, and it’s currently Sam’s turn to be the dreamer.

“I would hope, whenever we bring the curtain down, that Dean would find some peace [as well as Sam],” Singer concludes. “And if I have anything to say about it, he will.

“He’d like to finish this particular job and then go off and keep doing what he does.”

Supernatural airs Wednesdays at 9:00 p.m. ET on The CW.