The Winchesters have so far remained true to their promise to stay together in "Supernatural" season 11. But now it seems Sam and Dean will be separated by time – decades, to be exact.

The brothers have been busy hunting down various monsters in the past few episodes. But it's back to the bigger problem at hand as they discover a powerful weapon that could help defeat the Darkness. However, some time traveling will be involved.

We Got This Covered posted a synopsis for episode 14 and it teases that Dean (Jensen Ackles) will ask Castiel (Misha Collins) to send him back to the time when the Hand of God was last seen, which happens to be in 1944. But that's the least of his problems as Lucifer (Mark Pellegrino) is still using Castiel as his vessel. Lucifer (as Castiel) agrees to the plan and sends Dean back to World War II and to the submarine that sunk the Hand of God. It's safe to assume that the fallen angel only agreed to the plan because he has an agenda of his own. He continues his deception of the brothers, staying closed to Sam (Jared Padalecki) while they wait for Dean to return.

The trailer for the episode, titled "The Vessel," begins with Sam trying to clarify the "risks of time travel." But it seems Dean has safely made it to World War II as German soldiers are shown. The older Winchester, wearing a Navy uniform, reveals to the crew of the submarine that he's on a mission "for the future." Unfortunately, it seems like the mission is in danger as the submarine is shown being fired on just as the trailer ends.

The short clip also gives viewers a glimpse of the goings-on in Crowley's lair. Castiel is shown sitting on Crowley's chair. He taunts that "doggie wants to speak" as Crowley (Mark A. Sheppard) is pulled out from a cage where he's chained like a dog.

"Supernatural's" production team really went all out this time around as the episode's details really captured the essence of the time. Showrunner Jeremy Carver previously talked about the episode on Entertainment Weekly, calling it their version of "Das Boot" and describing it as "a really cool episode."

However, fans are wondering how long Lucifer can keep up his charade before the Winchesters become suspicious of his chosen vessel.

"Supernatural" season 11 will return to The CW with its newest episode on Feb. 17.