It's that time again, time for Doctor Who fans to hold their breath as the series heads into the season 8 finale.

How Much Danger Is Clara In During 'Dark Water'? Peter Capaldi Teases Perilous Episode

Kicking off this Saturday with "Dark Water," the two-part finale will bring back the cybermen and explore the mystery of the Gatekeeper of the Nethersphere. Like many of the previous season 8 episodes, the Steven Moffat-penned story will be far from light and airy.

"One of the perennial questions that faces all of us is, 'What happens when we die?'" Moffat said in a "Dark Water" preview. "I hope it's a lot nicer than this."

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The episode will end in a cliffhanger, meaning fans will have to tune into Nov. 8's "Death in Heaven" to find out how Twelve's (Peter Capaldi) latest adventure ends.

"It's two episodes that take us to the heart of the Doctor's struggles, meeting up with significant old enemies," Capaldi teased. "It's a big epic series finale."

Find out more when Doctor Who airs Saturdays on the BBC and BBC America. Click the video below to see a preview for "Dark Water."