This new season of Doctor Who gets better with each episode.
The fourth episode Knock Knock, written by Mike Bartlett, followed Thin Ice, Smile and The Pilot, which introduced Pear Mackie as new companion Bill.
Bill tries to send the Doctor (Peter Capaldi) off into time and space on his own in this story as she moves in to a creaky old house with her student flatmates. There’s a wonderful moment when the Doctor materliases the TARDIS around Bill’s gear at her old dig and then flies his trusty space and time ship to her new digs to help her move in.
The Doctor senses all is not right with the landlord (David Suchet) and the building, and is proved correct when Bill’s mates start to disappear.
Bill, and eventually the Doctor, make a horrific discovery which eventually leads to one of those wonderful moments when the Doctor begins to help. As he does this chilling horror story does a 180 degree turn and becomes a love story but, even then, all is not as it seems.
Suchet delivers a chilling performance which keeps you guessing until the end.
For all intents and purposes Knock Knock feels like a retelling of Neil Cross’s Series 7 story Hide, which saw the 11th Doctor (Matt Smith) and companion Clara Oswald (Jenna Coleman) investigate a haunted house which, too, ended in a love story.
The season arc, the Doctor and Nardole (Matt Lucas’s) mysterious guarding of a subterranean cabinet with what looks like Time Lord writing on it, isn’t as compelling as previous arcs. We’re clearly meant to think he’s keeping Missy (Michelle Gomez) locked up in there, but who knows? The Doctor!