The main problem with the episode is that it is full of uninteresting characters and the audience is not really given any reason to care about them. Bill decided to move away from home and in with five strangers. We get their names and then do not really learn anything else about them for the rest of the episode.
Bill and the five generic Millennials go off in search of a new home, but no suitable accommodations are found within their price range until they find a house that seems too good to be true. They immediately move in and spend their first night together trying to escape the house as it picks them off one by one.
Despite the fact that Bill’s roommates get very little characterization, we do see some development in her relationship with the Doctor. Bill hears the name “Time Lords” for the first time, which prompts him to tell her a little bit about his race. There is an amusing bit of their fantastic chemistry when she introduces him to her roommates and she thinks he looks old enough to be her grandfather. The best part of the episode is seeing them work together to solve the mystery. Companions work best when they are the Doctor’s link to humanity. This week Bill ended up putting the pieces together before the Doctor did. He tends to overlook important things, and this time Bill was there to correct him.
Overall, Peter Capaldi and Pearl Mackie saved an otherwise forgettable episode.