The Ripple Effect (short story)

 was the seventh Puffin eshort released to celebrate the 50th anniversary of Doctor Who. It was also published in the collection 11 Doctors, 11 Stories, and its sequels 12 Doctors, 12 Stories and Thirteen Doctors, 13 Stories.

Publisher's summary
When the TARDIS lands on Skaro, the Seventh Doctor and Ace are shocked to discover the planet has become the universal centre of learning, populated by a race of peace-loving Daleks. Ever suspicious of his arch-enemies' motives, the Doctor learns of a threat that could literally tear the universe apart...

Plot
Ace is helping the Doctor work on the console. They are stuck, with many other ships, in the Temporal Plexus. The Doctor devises a plan to escape, but the idea doesn't sit well with Ace. Ace sees a Police Box, and assuming it's a different TARDIS, asks the Doctor if all Time Lords have TARDISes. He says yes, and asks Ace why she asks. She says she saw a police box, but the Doctor dismisses the idea, blaming it on a temporal echo.

The Doctor and Ace escape the Plexus by causing a nearby star to Nova. In the process, he causes the Cloister Bell to ring. The Doctor explains they are being flung across space and time. Ace is relieved when she hears the sound of the TARDIS landing, but the Doctor says it is just an auto-land. They land on a planet, and when the Doctor opens the doors, they hear children playing. While the Doctor is tinkering with the console, Ace sees a Dalek glide through the open doors. The Doctor uses the quantum stabiliser to stun the Dalek. He notices that the Dalek doesn't have a ray gun, instead it just has two manipulator arms. Just then, a small crowd of children from assorted planets rush in. One girl, Tulana, confronts the Doctor. She takes the quantum stabiliser, and then three more Daleks come in. One blocks the door, while the other two approached their fallen comrade. One of the Daleks, Pytha, apoligises for his colleague, Sokar. He invites the Doctor for a tour of the academy after lunch. The group leaves, and Ace and the Doctor try to piece together what just happened. The Doctor concludes that they are on Skaro, however he knows that is not possible because Skaro doesn't exist anymore. He goes off to the bowels of the TARDIS to check the computer systems.

An hour later the Doctor finishes his research, and concludes that these are nice Daleks instead of the evil ones, instead of an earlier hunch that they were a renegade faction. Skaro has become the universal centre of civilisation, philosophy, democracy and art, similar to ancient Greece. They are then escorted to lunch by Tulana. Ace notices that the food they serve on Skaro is very different to the food on Earth, so she eats whatever Tulana does. When lunch has finished, Tulana takes them on the promised tour of the Academy. During this, the Doctor is scolded by a Dalek for his comment on ancient Greece. The Doctor tells Tulana about the Daleks he knows, but she explains that the accidental Neutron War caused them to mutate. She claimed that the Daleks the Doctor had met could be criminal Daleks, or even impersonators. Tulana takes them back to the main building, and rambles about the majestics of Skaro. The Doctor offers to take her on a tour of the jungle of Skaro, and Tulana agrees. They spend an hour zipping around Skaro. On their way back, the Doctor discovers a fleet of Dalek spacecraft, the surround Daleks fully armed. When the Doctor confronts Tulana, she simply says that the Daleks need some way to protect themselves from attacks. The Doctor returns Tulana to the Academy.

The Doctor spends the next few hours grumbling around the TARDIS, checking TARDIS archives and re-calibrating instruments. The Doctor eventually gives up, and is convinced by Ace to go to Gallifrey to talk to the Time Lords. Tulana is noticed on the monitor, and is let in by Ace. She hurriedly asks if the Doctor is going to see the Time Lords. The Doctor is amazed at how she knows he is going to Gallifrey. The Doctor doesn't want to take Tulana with them, but Tulana says she'll walk instead. The Doctor asks where she thinks she's going, and she replies that the High Council are at the hall to congratulate a Dalek medical team for operating on their Lord President. Tulana walks off, and the Doctor calls off his visit to Gallifrey, declaring that there is no point. Any change on the universe that big that happens without the Time Lords realising would be extremely dangerous indeed, he tells Ace.

The Doctor starts treating the Daleks like friends. Tulana is surprised, and asks why the Doctor has changed. He simply explains it on some sort of alternate timeline. He then explains to Ace that he has to fix it, or else the entire Universe could collapse from Space-Time decay. He converts the TARDIS into a vortiscope, and discovers the terrible truth that he caused the alternate timeline in their escape from the Plexus. He explains to Ace that the 'echo' she saw was actually their future, looping themselves back into the Plexus. The TARDISes were twisted together, and the energy caused when they were released was enough to cause the alternate timeline. He tells Ace they have to go back to the Plexus to fix it, but Ace doesn't want to say goodbye to Tulana and her new friends. Suddenly, a massive wave of decay ripples underneath them. Pytha requests for the Doctor's help, as the Universe begins to crumble.

Ace asks the Doctor what would happen to Tulana if they fixed things. He explains that Tulana was a Markhan, and their race was wiped out by the Daleks, two hundred years ago. The Doctor restores the chrono-dynamic parity, and him and Ace merge with the other TARDIS. His plan works, and after a quick back-track to Skaro, he discovers that the universe has been restored.

Characters

 * Seventh Doctor
 * Ace
 * Tulana
 * Sokar
 * Pytha

Continuity

 * The Doctor refers to the static electricity smell of the Daleks. (TV: The Daleks)
 * Ace remembers witnessing the Imperial-Renegade Dalek Civil War. (TV: Remembrance of the Daleks)
 * Ace initially assumes all TARDISes look like police boxes, until the Doctor explains how his TARDIS's chameleon circuit is broken. (TV: An Unearthly Child)