Goodbye, Sarah Jane Smith

The story starts off with Mr Smith telling Sarah Jane that a meteor is heading towards Earth. Sarah Jane, Rani and Clyde travel to the meteor to stop germ pathogens from escaping. Just as Rani is about to deactivate it, another woman destroys the germs with similar equipment. The mysterious woman exclaims that she is "saving the world", and runs off. The team chase after her but she escapes, after which Clyde says to Sarah Jane, "She's exactly like you."

The team returns to Sarah Jane's house, but spot the strange woman at a house down the road, into which she has recently moved. They go round to investigate and discover that the woman's name is Ruby White. Ruby rudely orders them to leave and they return to the attic, where they discover that a mysterious race known as the "Dark Horde" have come to Ealing. They are then alerted by Mr Smith that the Dark Horde have locked onto the location of Sarah Jane's house. Sarah Jane tells Mr Smith to redirect them to somewhere else, and gives Clyde a gun before they all head off to an abandoned warehouse.

When they get there, Sarah Jane scans for the Dark Horde and finds that there are three aliens, an advance party of warriors. While Sarah Jane is scanning, a laser blast heads towards them; the team hide behind a broken van. The blasts are coming from the Dark Horde's spears.

Sarah Jane asks Clyde to pass her the sonic lipstick so they can use a "scanblind" device to get rid of the Dark Horde, only for Clyde to tell her that, as per her instructions, he brought an uncharged blaster. Clyde then asks her what Plan B is, but Sarah Jane tells him that there is no Plan B. The Dark Horde approach the team and threaten them. Before they are shot, however, Ruby White calls to them, holding two small "scanblinder"-like spheres. Ruby then shouts, "Wait till you see what I've got for you!"

Ruby throws the two spheres to Rani and Clyde, pulling a larger one from her pocket. They make a triangular force-field, then the Dark Horde warriors suddenly teleport away. Ruby now expresses her admiration for Sarah Jane's work, and later they all return to the attic, where the team name Ruby's hand-held AI "Mr White".

Ruby explains that she was on an archeological dig, on which she dredged Mr White out of a swamp in New Zealand. Clyde and Rani leave the house, and Sarah Jane and Ruby continue talking. Whilst talking, Sarah Jane mentions The Doctor, but almost forgets his name. She wonders if she is ill, and so later asks Mr Smith to perform a "medi-scan" on her. Mr Smith tells her that she is very ill and there is no treatment. Sarah Jane, believing herself no longer capable of doing her work, offers her life and lifestyle to Ruby. Ruby accepts the offer; Sarah Jane removes her voice commands from Mr Smith's system.

Ruby now reveals her true nature, sneeringly calling Rani "wonderful and brilliant", and Clyde "plucky", and openly mocking Sarah Jane. Confused, Sarah Jane decides to call Luke, but Ruby refuses to allow Mr Smith to place the call.

Sarah Jane nearly faints, and is grabbed by Ruby. Ruby presses a button on her bracelet and then both she and Sarah Jane disappear. They appear in what Ruby calls her "secret cellar". In the cellar is a large red bulging mass, which Ruby claims is her stomach, hungry for Sarah Jane's soul. Ruby reveals that she is responsible for making Sarah Jane ill. Ruby chains Sarah Jane to a wall, revealing that she is a Qetesh, a race of aliens who survive by devouring the souls of others; she sought Sarah Jane's soul because Sarah Jane's life is "the most exciting one on the planet".

Ruby drains energy from Sarah Jane's body, and exclaims that she will feast on the Earth and many other planets.

Ruby threatens Sarah Jane with her stomach. She tells Sarah Jane that she will track aliens, just as Sarah Jane did, but that instead of fighting against them, she would help them.

The next day, Rani and Clyde go to Sarah Jane's house. Finding the door ajar, they go up to the attic and are confronted by Ruby. Ruby plays Rani and Clyde a clip of Sarah Jane handing over her life to Ruby. Watching this in Ruby's cellar, Sarah Jane shouts that it is not her. Clyde becomes angry, and tells Ruby to "shut up", and then storms out of the house. Ruby vanishes to her cellar.

Clyde becomes angry with Rani, telling her to stay away from him. She runs home in tears. Gita, comforting Rani, tells her that Sarah Jane would never run off.

Clyde returns to the attic, and asks Mr Smith where Sarah Jane is. Mr Smith is unable to reply clearly, but manages to tell Clyde "beware". Ruby enters, and Mr Smith says "R", indicating that the culprit's name starts with "R": Ruby.

Attempting to flee, Clyde is grabbed by Ruby. Mr White shuts Mr Smith down, and then Ruby transports Clyde and herself to a round room. The room is in space, and was Ruby's prison until she turned it into her ship. Ruby leaves Clyde, but first informs him that the only air in the room is the air that they brought in with them.

Meanwhile, Rani attempts to phone Clyde, but can't get through. The doorbell rings; expecting Clyde, Rani runs to the door. At the door is Luke. Luke, Rani, and K9 ascertain that Ruby and Mr White are both of Qetesh origin; Mr White is a "5-D" holographic device. The realisation of Mr White's origins also reveal that the meteor and invasion were holographic.

Rani goes up to the attic, and finds Ruby scanning the sonic lipstick. Rani hugs Ruby, surreptitiously placing her phone on the table next to Mr White so that K9 can shut the alien AI down. Rani pretends to cry to distract Ruby, then grabs the sonic lipstick. She starts to run away, but stops when she sees Ruby pick up and crush the phone. However, it is too late; K9 has managed to restart Mr Smith.

Suddenly, Clyde reappears and points a gun at Ruby. However, he has no intention of firing it. Instead, he asks Mr Smith to place Ruby in a containment vortex. Ruby, confident that the force field won't hold her for long, attempts to flee using her bracelet, but is unable to. Luke then asks Mr White where Sarah Jane is, and finds that she is at Number 46, Old Forest Road, with Ruby's stomach. The force field starts failing, and Ruby warns the children that they had better flee. She goes to grab Mr White, but is electrocuted in the process.

Clyde and Rani find Sarah Jane almost dead; Rani uses the sonic lipstick to destroy the chains holding Sarah Jane, and they lift Sarah Jane to her feet. Ruby comes down the stairs, and approaches the trio. Her stomach grows teeth and snaps at Sarah Jane, Rani, and Clyde. Luke runs in, and offers Ruby one chance to leave the planet. When Ruby doesn't listen, he uses his phone to instruct Mr White to activate the hologram.

Outside, Gita and Haresh are standing; Haresh tells Gita that Sarah Jane would not run off, and that Rani is probably with her right now. A rumbling noise makes them look up: they see large meteors falling through the sky.

Ruby screams as more meteors appear to fall into the River Thames, the widespread terror overloading her capacity to absorb it. At the end of the proceedings, all of Sarah Jane's strength returns to her as the stomach shrivels. The meteors disappear, much to the relief of Gita and Haresh. Sarah Jane sends Ruby back to her prison in space; Ruby vows to make the Earth suffer. The prison's gravity lock disengages, however, and the prison is sent hurtling into the sun. When Clyde walks up to the shrivelled stomach, it spurts pink goo in his face.

Back on Bannerman Road, Sarah Jane puts Mr White into her safe. A horn beeps outside; Sarah Jane tells the teenagers that it is "their ride". Sarah Jane, Clyde, and Rani go downstairs, to find Luke in his yellow VW. Sarah Jane says to herself, "Yes, there are amazing things in the universe, but they've got some stiff competition on Earth!"

• Ruby describes the so-called "Ealing triangle", referring to astrologer Martin Trueman in Secrets of the Stars, the Bubble Shock! factory in "Invasion of the Bane", "rhinos" (Judoon Captain Tybo) in a police car in Prisoner of the Judoon, and the alien plant life of The Gift.
• Sarah Jane tells Ruby about when she met the Third Doctor while chasing a news story in The Time Warrior.
• The episode continues the tradition of one serial in each of the first four series bearing Sarah Jane's name in the title; it is the first such serial not to feature The Trickster as the guest villain.[3]