Doctor Who will dive into the deep as season 9 pushes forward.

'Doctor Who' Season 9 Spoilers: Clara Is Officially Out; Jenna Coleman Teases 'Really Cool' Exit

Once the events of the two-part premiere disappear into the past, Twelve (Peter Capaldi) and Clara (Jenna Coleman) will sink beneath the waves for episode 3. "Under the Lake" will delve into the gloom as ghosts of the recently deceased overrun a mysterious underwater base.

"When an Underwater Base comes under attack, the Doctor and Clara must save the frightened crew and defeat an impossible threat," the BBC teased. "But what is behind these terrifying events? And can they really be haunted by ghosts?"

'Doctor Who' Season 9 Spoilers: All Episode Titles Announced, Will David Tennant Return For The Finale?

We've seen alleged "ghosts" before, and the Doctor always manages to find a scientific explanation for the supernatural. Can Twelve uncover the truth once more, or will viewers been left with a bone-chilling cliffhanger?

"It's impossible! It's evil! I hate it! It's astonishing! I want to KISS IT TO DEATH," showrunner Steven Moffat gushed, according to Spoiler TV.

Find out more when Doctor Who airs Saturdays on the BBC and BBC America. Click the video below to see a preview for the series' next episode, "The Witch's Familiar."

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Doctor Who, Television, BBC