The Doctor (Peter Capaldi) will go missing in action while a mysterious alien force attacks the world in the upcoming season of BBC's "Doctor Who."

Cultbox reports that the premiere episode titled "The Magician's Apprentice" will see Clara (Jenna Coleman) trying to search for him "when the skies of Earth are frozen" due to the invading super power villains. The official synopsis released by the network reveals that the Doctor is trying to hide from something, perhaps an old enemy. His past misdeeds and foes will reportedly come back to haunt him, endangering his life and Clara's.

In an interview with Entertainment Weekly, Capaldi hinted that something big would happen in season 9 that would shock the fans of the science fiction series. When asked to compare his character in the new installment from the last, he said that the Doctor will be more adventurous.

Capaldi said, "He's throwing himself into life with a newfound hunger for adventure. He's in pursuit of joy and grabbing every thrill that he can along the way. But I sense him running from something, that even he does not yet understand."

The actor also teased that the Doctor would make a grave mistake that has "cataclysmic repercussions" and this would push him to go into hiding. He shared that there would be "an epic sweep" this season, as "some very scary creatures" were slated to cause chaos in the world.

Telegraph reveals that the Doctor will be encountering the Daleks, a race of mutant space robots which he encountered back in 1963. The second episode titled "The Witch's Familiar" will purportedly see the protagonist facing his long-time nemesis while trapped in a Dalek city "with no Tardis and no sonic screwdriver." According to the recently released trailer, the Doctor may meet the young Davros, the evil creator of the robots.

"Doctor Who" season 9 will premiere on Sept. 19 on BBC.