The Caretaker was the sixth episode of the eighth series of Doctor Who produced by BBC Wales. It had the Twelfth Doctor and Clara Oswald deal with an alien threat to Coal Hill School, leading to both Danny Pink and Courtney meeting the Doctor and subsequently discovering his true nature.
It also contributed to the “Promised Land” arc by introducing an underling of Missy, and giving her location a new name, the Nethersphere.
Building on the experience of writing The Lodger and Closing Time, Gareth Roberts and Steven Moffat tried to match the former for threat, feeling there was an excessive amount in Closing Time, which had included back-story for the antagonists at the expense of other themes. For this reason, it was decided that the first draft had the right amount of threat and that it would be unnecessary to add more later.
The episode begins with a montage of Clara balancing adventures in the TARDIS and her relationship with Danny. After an adventure on a desert planet, Danny notices she’s developed a tan since he last saw her, while an encounter with fish people leaves seaweed in her hair during a date. These two lives collide one morning when Mr Armitage introduces Coal Hill School’s new caretaker, John Smith — in reality, the Twelfth Doctor, who is clad in the kind of brown overall coat that a caretaker would wear, and carrying a rather worn-looking broom. Meanwhile, CSO Matthew investigates a mysterious noise coming from a rundown building, caused by the Skovox Blitzer, which disintegrates him on sight.
When working on a substation, Danny and the Doctor conflict over what Danny teaches. Danny claims to have been a soldier who now teaches maths, while the Doctor instead thinks he teaches PE, as this would make more sense due to him being a soldier. But the Doctor doesn’t realize Danny is Clara’s boyfriend, instead thinking this is Adrian, who resembles his previous incarnation. The students are aware of their relationship, evidenced by graffiti mocking it.
Later, the Doctor is working in the caretaker’s room, when student Courtney Woods finds him and the TARDIS. She too conflicts with the Doctor, and on her way out makes a remark to Clara about Danny. Here, the Doctor shows Clara a hologram of the Skovox Blitzer. Knowing it will eventually attack to destroy Earth, he aims to send it away from the planet.
The tools he’ll use to do this are an invisibility watch to prevent the Blitzer scanning him and as non-threatening alien technology to lead it to him, and chronodyne generators to send it billions of years into the future through a vortex.
After Clara leaves the TARDIS, she and Danny make plans for after parents’ evening in a few days, while the Doctor follows the Blitzer’s signal. He and it meet in the hall, where the generators have been turned from green to red because of Danny’s interference. While the Blitzer is sent through a vortex into the future, Danny’s intervention means it will return in only three days. After the chaos, Danny realizes Clara’s lived a lie to him. She tells him the truth: she’s human, but the Doctor’s an alien. They travel through time and space in a TARDIS, which is disguised as a police box, but is bigger on the inside. The Doctor shows Danny the inside of the TARDIS, and Clara takes him home to deal with the shock.
Danny recaps what Clara’s told him: the Doctor used to resemble Adrian, but changed into a Scottish caretaker. He travels with Clara in-between her time with Danny. He asks her why she travels with him, which she attributes mostly to the wonders that she experiences. Danny struggles to accept whether or not Clara loves the Doctor romantically, which she denies.
Parents’ evening arrives, and Clara gives Danny the invisibility watch. He turns invisible, and she takes him with her into the TARDIS so he can watch her interactions with the Doctor. He has nearly finished building a device to fight the Blitzer. As Danny remains invisible, the Doctor suddenly suggests that he and Clara go off somewhere. She reacts worriedly, and Danny realizes that the Doctor somehow knows that he is there. He turns off the watch, becoming visible. The Doctor reveals that the invisibility shield does not work on Time Lords. Seeing the Doctor’s title as a Time Lord to be pompous, he mockingly responds to the Doctor’s demand to leave the TARDIS like a soldier taking an order. This brings out the militant side of the Doctor, and the two men trade insults in a heated confrontation. Courtney sees Clara and Danny leave the TARDIS. She asks the Doctor what’s really in the police box, which he shows her.
As the parents arrive, the Blitzer unexpectedly returns from the vortex one day early. The Doctor’s device detects it. He summons Clara through the door, prompting her and Danny both to leave. Courtney’s parents, who were talking to Danny, express that their daughter was right about the two teachers’ relationship. Meanwhile, the Doctor discusses his plan: Clara attracts the Blitzer with the sonic screwdriver, and it chases her to the caretaker’s room, where the Doctor speaks to it through the device he’s built. It is a communication device that makes the Blitzer think the Doctor is its superior. He tells Danny to do one very important thing: keep out of their way. The plan seems to work, and the Doctor tells the Blitzer to deactivate. It obeys, pending a final authorization code. The Doctor needs time to prepare the code. Instead of deactivating, the Blitzer has begun a self-destruct count down. He tells Clara to distract it while he hurriedly tries to prepare the code, but she is unsure what to do. Just then, Danny yells out to the Blitzer. He runs and jumps over it as it fires its lasers at him. This distracts it long enough for the Doctor to give the final code, deactivating the Blitzer. Danny reveals to Clara he was following her with the watch and vows to protect her. He tells her that he only needs to do one thing, which the Doctor confirms: to prove he’s worthy of Clara.
The Doctor takes the Blitzer into space and ejects it from the TARDIS, taking Courtney on her first trip. Unfortunately, Courtney is unable to cope with the immensity of the universe and finds herself feeling rather ill — whereupon she rushes back inside and is sick. Back on Earth, Clara and Danny watch television. Danny tells her that the Doctor reminds him of previous commanders he has known, who push their soldiers to get them to do more than they realized they were capable of. Clara obeyed the Doctor without being scared. Danny worries that the Doctor might push her too far. He insists that Clara promises to tell him if that happens.
Elsewhere, CSO Matthew is in a long white office corridor with many doors on either side of the hallway. He doesn’t realize that he has been killed, and is talking to a person named Seb at an information desk. Seb tries to break the news gently, having encountered many new patrons to the afterlife because of the Skovox Blitzers. He tells Matthew that the place has many names, including the Promised Land. Seb personally prefers to call it the “Nethersphere”. They notice Missy appear from one of the doors. She gives a stone-faced glance. Seb tells Matthew that Missy is quite busy at the moment, before asking him if he has any questions about his new existence in the Nethersphere.