Doctor Who is two episodes into its 10th season, and still exploring the relationship between the Doctor (Peter Capaldi) and his new companion, Bill (Pearl Mackie). Last week’s ‘Smile’ found the two on a planet inhabited only by robots who communicate via emoji – a perfect freak-of-the-week style episode that allowed Bill to shine as she continues to explore the wonderful new world of time travel.

Next week, however, things start to look a little bit darker. The mysterious Vault may not come up again (or may make another brief cameo), but Bill is starting to wonder about the Doctor’s morals. In a new trailer, the BBC reveals a new destination in time and a new monster to fight.

The trailer shows Bill and the Doctor heading back in time, to Regency England. The two are exploring London – and discovering a few historical inaccuracies – as Bill asks the Doctor about the rules of time travel. However, they quickly discover ’lights beneath the ice’, a monster hiding under the frozen Thames, and the Doctor can’t help but go and investigate.

At the very end of the trailer, a concerned Bill asks the Doctor, “Have you ever killed anyone” with a quaver in her voice – an interesting question, as long-time fans of the show know that he is far from innocent. It seems that as well as the usual weekly monster, ‘Thin Ice’ is going to be giving Bill a better look at the darker side of the Doctor.

Doctor Who often goes back in time, as well as forward (and to distant planets), especially with new companions who have always dreamt about seeing what life was like at a different period in history. ‘Thin Ice’ promises to follow in the footsteps of previous historical episodes, with lots of wonderful costumes and fun twists on historical periods (and even figures, although this time it doesn’t look like there will necessarily be a specific person who the Doctor visits). It’s also going to be interesting to see how the Doctor answers Bill’s question, and how that changes their budding relationship.

As always, there is sure to be more to the monster beneath the Thames than meets the eye, and a surprise villain who is controlling (or at least, feeding) it, but we’ll have to wait until Saturday to discover exactly who it is for ourselves.

Doctor Who continues next Saturday with ‘Thin Ice’ @9pm on BBC America.

Next: Doctor Who Season 10: What’s in the Vault?

Source: BBC America