Fear the Walking Dead Dives Into a Nuclear Submarine in 615 Sneak Peek

Morgan (Lennie James) and Grace (Karen David) might not make it off a nuclear submarine in a scene from the penultimate episode of Fear the Walking Dead's sixth season. When we saw them together in "In Dreams," Grace was about to give birth and convinced Morgan to give up the key that Teddy (John Glover) and his followers have been after all season. As Teddy finally revealed to his prisoner Alicia Clark (Alycia Debnam-Carey) in "Mother," the key will launch a missile from the beached submarine washed ashore in Galveston, Texas, and end everything he hates about the world above.

When Morgan and Strand (Colman Domingo) mount a desperate mission to stop the missile in Season 6 Episode 15, "USS Pennsylvania," it's going to take everyone working together: Morgan and Strand, Dwight (Austin Amelio) and Sherry (Christine Evangelista), June (Jenna Elfman) and her recently discovered father-in-law John Dorie Sr. (Keith Carradine), and a hardened Grace who doesn't want to talk about the devastating loss of her stillborn daughter.

"I haven't pushed it because I understand the pain. But if we don't talk now we might not get another chance," Morgan warns Grace. "What needs to be done here to stop them, I might not make it off the boat."

"We," Grace tells him. "We might not make it off."

Before it washed ashore in Galveston, the USS Pennsylvania was manned by a crew that included Walter (Damon Carney), the original owner of Morgan's key who was beheaded by bounty hunter Emile (Demetrius Grosse) in the Season 6 premiere, "The End Is the Beginning." Most of Walter's crewmates — but not all, as we'll soon find out — perished in the early days of the apocalypse, a story that will be told in the digital spin-off series Dead in the Water.

Announced by AMC in March, the digital series tying into Season 6 of Fear "tells the story of a submarine crew fighting for survival, cut off from the surface world just as the apocalypse hits, becoming a nuclear-fueled walker-filled death trap with no way out."

"In this episode, the cool thing is we're all coming together as a company trying to fight people who are trying to destroy the world," Domingo says in the trailer for Fear's penultimate episode of the season airing in two weeks. "It becomes super epic, we all have to get our icon on and get our superhero on. I think it's super exciting to see the kind of hero that Victor Strand believes he can be, and we'll see how people are able to handle the pressures of what's ahead of us."

Follow the author @CameronBonomolo on Twitter for all things TWD Universe. "USS Pennsylvania" premieres Sunday, June 6, at 9/8c on AMC.