Journey Blue and Colonel Morgan Blue

A rebel fighter called Journey Blue is in a space shuttle that is being shot at by a Dalek spaceship. She is unable to save her brother as the rebel space shuttle explodes and she appears in the TARDIS console room and is met by The Doctor.

She points her gun at The Doctor, demanding that he take her back to her command ship. When she finally asks nicely, he complies and the TARDIS materialises aboard the rebel’s command ship, the Aristotle, a base for the Combined Galactic Resistance, the Galaxy's united front against the Daleks. There he is greeted by Journey Blue's uncle, Colonel Morgan Blue, who thanks The Doctor for saving his niece, but declares that he must be killed in fear he is a Dalek spy. However, The Doctor is saved when Journey Blue declares that, as he is a doctor and that so could help their patient. This is revealed to be a war-torn Dalek that was found floating through space who has appeared to have turned good. The Doctor at first is uninterested in helping the creature, grimly declaring that Daleks cannot be good, until that is until the Dalek voices its desire to slaughter the rest of its kind.

Meanwhile at Coal Hill School, on Earth, new Maths teacher Danny Pink, a veteran of the war in Afghanistan with emotional scars from his past, is introduced to Clara Oswald, who invites him to a leaving party for one of their colleagues. Feeling awkward due to an obvious connection between them, Danny Pink declines, but when Clara finds him in his classroom despairing over his actions, she invites him out for a simple drink instead. Given another chance he agrees. Clara returns to her office, where she discovers The Doctor, standing there with the coffee she sent him for three weeks ago when they were in Glasgow (see "Deep Breath"). The Doctor tells Clara that he needs her help urgently. He also takes the liberty of asking her if she thinks he is a good man but Clara replies that she does not know.

The Doctor

The TARDIS materialises back on the rebels' command ship, where The Doctor explains that a malfunction in the Dalek, as well as giving it a conscience, is also killing it. Fascinated by the idea of a Dalek with a conscience he agrees to help it. Colonel Blue details a plan to miniaturise The Doctor, Clara, Journey and two rebel soldiers, Ross and Gretchen, so they can enter the broken Dalek, which The Doctor has nicknamed 'Rusty', to see if they can determine what is making it good.

Entering through the eyepiece, they begin exploring the upper part of the Dalek. As they explore The Doctor shows the group Rusty's artificial memory drive which filters out good memories and reinforces bad ones. The Doctor takes the liberty of asking Rusty what made it turn on its own kind, to which it says he had witnessed beauty in the galaxy, including the creation of a star, and that the Daleks must be destroyed for wanting to destroy that beauty.

A Good Dalek?

Realising that they have to descend to the lower parts of the Dalek, Ross shoots a griphook into the floor so as to set up a zip line. This though damages Rusty's body and so triggers the release of antibodies. Realising that he cannot save Ross from the attacking antibodies, The Doctor gets to him swallow a pill that will allow him to locate where the antibodies store his obliterated remains - this is a waste centre, in the lower regions, and where The Doctor correctly guesses that nothing will be guarded there.

Having escaped from the antibodies The Doctor, Clara, Journey and Gretchen head to the Dalek's power centre and an area of high radiation. There The Doctor discovers a large crack in one of the batteries that is leaking the deadly radiation which he deduces is causing the malfunction within the Dalek, as well as both killing Rusty and now them. The Doctor uses his sonic screwdriver to seal the crack, fixing Rusty in the process. However, this causes the Dalek to immediately return to its original programming so losing all the good within it.

Now that Rusty is fixed the Dalek breaks from its chains. Colonel Blue and his men are helpless as the Dalek begins exterminating the rebels. Determined to aid the Dalek cause it contacts the Dalek spaceship so revealing where the rebel’s command ship is hidden. This releases more Daleks with the aim of destroying the rebels. Inside Rusty, The Doctor though is ecstatic as his belief that there is no such thing as a good Dalek is restored. Clara, enraged by The Doctor's apathy, slaps him on the face before pointing out to him that what they have learned is not that there is no such thing as a good Dalek but that it is indeed possible.

Clara at Coal Hill School

Inspired by Clara's words The Doctor realises that the good parts of Rusty can be restored. They split up, with Clara and Journey heading to the artificial memory drive to reawaken memories of the Dalek's past that are now being suppressed, and The Doctor heading to the Dalek itself to try and reason with the Dalek. The other remaining soldier, Gretchen, sacrifices herself to set up the griphook to get Clara and Journey to the mind of Rusty. In doing so she is destroyed by the antibodies. But instead of dying Gretchen awakens in 'heaven', with the mysterious woman named Missy, the same woman who greeted the Half-Face Man in "Deep Breath".

Meanwhile still inside the Dalek, Clara manages to deduce how Rusty's memory core works and reactivates all of his suppressed memories. With this The Doctor is able to form a psychic link with Rusty and transfer all of his memories. However instead of reawakening its good side Rusty is inspired with The Doctor's own deeply-rooted hatred towards the Dalek race, and starts exterminates his fellow Daleks as they attempt to destroy the rebel command ship. As Rusty slaughters the rest of the Daleks on the command ship, everyone is returned to their proper size. On leaving the inside of the Dalek, Rusty tells the Time Lord that The Doctor himself is a good Dalek. The Doctor though is upset that the Dalek saw only darkness within him and that he was not able to recreate the good Dalek. With all the Daleks destroyed Rusty departs the command ship sending a signal to the Dalek spaceship, causing it to believe the rebel's command ship has been set to self-destruct, causing the to the Daleks spaceship to retreat. Rusty rejoins its kind vowing to continue with his mission to destroy the Daleks.

As The Doctor and Clara prepare to leave in the TARDIS, Journey asks to join them as a companion, but The Doctor turns her down. He recognises the good in her, under the battle-hardened exterior, but the fact she is a soldier troubles him. She accepts The Doctor’s decision, knowing that he is only doing what he feels is best.

The Doctor returns Clara to Coal Hill School, moments after she left, and she tells him that, although she is still unsure of whether he is a good man, she knows his intentions are well meant - which is the important thing. After changing into new clothes for her evening with Danny, Clara is met by Danny in a school corridor. He tells her he is glad that the fact he is an ex-soldier hasn't put her off. Remembering The Doctor's treatment of Journey, she is determined not to adopt The Doctor's feelings about soldiers.