The penultimate episode of Doctor Who series 10 came bundled with all sorts of surprises, from John Simm returning as the Master after spending an episode in disguise and Missy apparently rejoining the forces of evil, all the way to companion Bill Potts (Pearl Mackie) being forcibly converted into Cyberman form.

And it seems like the twists are only set to continue in this Saturday’s finale, with series 10 finale guest star Samantha Spiro (who plays a woman called Hazran defending children from the Cybermen) hinting to RadioTimes.com that nothing is as it seems in the last episode.

“What little hint can I give?” Spiro pondered when asked for clues about 12th episode The Doctor Falls. “Nobody is as you think they are – or people aren’t necessarily what they think they are.”

But what could this mean? Could we have more surprise returns in the same realm as John Simm’s Master, perhaps with classic characters disguised as new faces (following on from hints that River Song or the Doctor’s granddaughter Susan could be back this year)?

Or does the quote refer to Michelle Gomez’ tormented Missy, who seems to have turned back to the dark side? With the Doctor still hoping to redeem her, perhaps she’s not as bad as she thinks she has to be after all…

Or maybe it’s something else entirely, related to the character of Peter Capaldi’s Doctor as he’s pushed to the edge by the terrible situation he finds himself in. Could he be about to make a decision that will surprise anyone who thinks they have the measure of him by this point?

Whatever the truth, we’re excited to see the whole thing unfold – and according to Spiro, the finished episode is well worth the anticipation.

“Because this is the final episode there’s some fantastic epic pieces that Peter deals with as the Doctor,” she told RadioTimes.com, “that I found really quite a privilege to witness; it really took my breath away.

“I think he’s brilliant,” she added. So do we…

Doctor Who series 10 concludes on BBC1 on Saturday 1st July