The next episode of "Doctor Who" season 9 puts the Time Lord in another one of his most challenging encounters yet. In the installment ominously titled "The Zygon Inversion," the Doctor races against the clock to save the whole city from the shape-shifting alien race terrorizing the place.

The Zygons are far more powerful and dangerous now. In a BBC clip, Peter Capaldi aka the Time Lord revealed that the enemies "are able to transform into the appearance of loved ones," giving them the ability to "read the minds of their potential victims" and making them more difficult to kill.

With the Zygons evolving and now capable of taking the form of basically any human, the Doctor will have to be extra careful in choosing whom to trust. In the promo, it is shown that a Zygon even imitates his companion Clara, although the true evil beneath is seeping through.

In this "Doctor Who" season 9 episode, viewers will see a sinister version of Clara, who seems to have come across an important instrument that will help the Zygons instigate and dominate a war.

Clara comes across a video of Osgood stating the unspeakable horrors the Osgood box, which she made along with a clone of hers, can do. "The Osgood box can wipe out humankind," Osgood can be heard saying as bad Clara goes on the move. "The Osgood box can start a war," she then adds.

It looks like in this "Doctor Who" season 9 installment, Clara will indeed make use of the Osgood box. It remains to be seen what the Time Lord can do and will do to stop her, but what's sure is that Clara's sinister Zygon does not concern herself with who's going to die.

"Doctor Who" season 9 episode 8 "The Zygon Inversion" airs Nov. 7 at 9 p.m. ET on BBC America.