Doctor Who: Where's the Exterminator When You Need Him?

Ultimately, the story here is one that is achingly familiar to Doctor Who, and it more or less boils down to the idea that one life is not more important than another, that the preservation of one person's life doesn't outweigh the lives of many.

In last week's "Thin Ice," the Doctor poignantly addressed this in his speech about the young orphan boy's life being no less valuable than the man who was born into wealth and comfort, and that's again true here.

The first thing Bill does when moving into her new bedroom is show off the space to a framed photograph of her mother, and then hang it on the wall next to her bed.

Amy (Karen Gillan) and Rory (Arthur Darvill) didn't travel with the Doctor constantly during their years with him, and Clara (Jenna Coleman) was a school teacher who had relationships outside of her own travels with the Doctor.

After last week ended with someone knocking on the vault door, this week we learn that whomever is inside now has a piano to pass the time, and the Doctor is bringing them food, noting that they're both prisoners stuck in this unpleasant situation so they might as well hang out.