Flip-Flop (audio story)

 was the forty-sixth story in Big Finish's monthly range. It was written by Jonathan Morris and featured Sylvester McCoy as the Seventh Doctor and Bonnie Langford as Melanie Bush.

It was notable for its highly experimental format. Each of the two discs (which each contained two episodes) could be listened to in whatever order the listener chose. The serial detailed what happened when the Doctor was coerced into changing the past by altering the fate of the president of a human colony, but offered no conclusions about which of the versions of history was the "correct" one, allowing the listener to decide for themselves. Additionally, these circumstances mean that neither Black nor White version of the story have a proper conclusion with one forming the foundation of the other, stuck in a circular narrative that only the Doctor and Mel are able to leave.

The play was further notable for being the closest the Quarks have ever come to returning to performed Doctor Who since The War Games. Though never heard, the Quarks are essentially the of the story and are mentioned at least once in each episode. From the Doctor and Mel's perspective, the events of Flip-Flop were merely a side-trip from their current "mission" to defeat the Quarks aboard the space yacht Pinto.

Publisher's summary
Christmas Eve in the year 3060 and the planet Puxatornee is home to a prosperous human colony.

A space craft has arrived in orbit carrying the Slithergees, a race of obsequious alien slugs. Their home world has been destroyed and they are humbly requesting permission to settle on the first moon.

And if they don't get permission, then they are humbly threatening to declare all-out war.

The future hangs in the balance. The decision rests with Bailey, the colony's president — but she has other things on her mind...

Christmas Eve in the year 3090, and the planet Puxatornee has changed beyond all recognition.

The Doctor and Mel arrive, on a completely unrelated mission to defeat a race of terrible monsters, and soon discover that something rather confusing has been happening to history...

Part one (White Disc)
The Doctor and Mel land on Puxatornee on Christmas Eve, 3090, in search of Leptonite crystals. The Doctor is disturbed to find the war-ravaged colony on its last legs.

Security agents Stewart and Reed promptly arrest them as self-confessed Slithergee spies. To their surprise, they are soon rescued from jail by an entirely different Stewart and Reed who are killed before the Doctor and Mel can ask what's going on and why everyone seems to know them.

Confusion ensues, with paranoid President Mitchell ordering his security forces from one side of the city to the other chasing conflicting reports of the escapees' whereabouts. Meanwhile, Mel and the Doctor discover the laboratory of Professor Capra, inventor of a one-way time machine. The Doctor vows to stop the humans from meddling with their own history.

Mitchell plans to send Lieutenant Stewart and Lieutenant Reed back in time to save President Bailey, whose assassination 30 years ago led to war with the Slithergees. The humans won that war, but at great cost. Radiation, poisoned fields and martial law have made life on Puxatornee unbearable.

Mel and Stewart are flung back to 3060 by Capra's machine, which then overloads and destroys Puxatornee in 3090. The Doctor and Reed escape in the TARDIS before that happens, but are too late to stop Stewart from killing Clarence, Bailey's supposed assassin. The Doctor can't bring himself to kill President Bailey to restore history. Reed and Stewart tell President Bailey that they came from a terrible future where war ruined Puxatornee, and they insist she make peace with the Slithergees at any cost.

Part two (White Disc)
The Doctor takes Stewart and Reed forward to Christmas Day 3090 in the TARDIS, but history has now changed. President Bailey, the "Great Appeaser," has capitulated to all the Slithergees' demands, allowing them to occupy not only Puxatornee's moon but eventually the planet. Humans have become slaves, and their culture is being erased even as the Slithergees demand retribution for "hate crimes" and discrimination.

Officers Stewart and Reed are horrified. This is not the future they wanted. They demand the Doctor take them back to the previous night, Christmas Eve 3090, to stop themselves just before they embarked on their mission to save Bailey. He complies, but he can't return them to the timeline they've erased. Stewart and Reed are killed by Potter, an officer who served under them in their own history, but who is working for the Slithergees in this one. The Doctor and Mel, meanwhile, re-encounter the alternate Stewart and Reed, rebels against Slithergee occupation. The rebels don't recognise them, but learn from a careless comment of Mel's that the Doctor has a time machine.

The Doctor and Mel realise that not only are there alternate versions of Potter, Stewart and Reed running around, but that their own counterparts will shortly materialise in the same place where they landed. Having secured the Leptonite crystals they need, they rush back to their TARDIS and dematerialise in the nick of time, trusting that the alternate Mel and Doctor will sort out Puxatornee.

Part three (Black Disc)
The alternate Doctor and Mel land on Puxatornee on Christmas Eve, 3090, in search of Leptonite Crystals. Mel is disturbed to find humans enslaved to the Slithergees.

Potter and his Slithergee master promptly arrest them as dissidents. He takes them to Professor Capra for interrogation. Two rebels, Stewart and Reed, burst in and free them. To Mel and the Doctor's surprise, the strangers seem to know who they are. They want to use the Doctor's time machine to go back in time and kill Bailey before she gives in to the Slithergees' demands.

Bailey, meanwhile, has lost faith in her deputy, Mitchell, whom she suspects has been serving the Slithergees all along. She believes he staged the assassination attempt 30 years ago and hired two imposters to dissuade her from war. The quarrel ends with Bailey dead. Suicide, Mitchell tells the Slithergee Community Leader, although she apparently tried to shoot him. The Community Leader hails Mitchell as the new president, but soon kills him, making Puxatornee the "Planet of the Slithergees".

After Stewart threatens to shoot Mel, the Doctor has no choice but to take him and his associate back to 3060. Stewart and Reed kill Bailey's secretary, Clarence, then execute President Bailey for crimes she has yet to commit. Stewart leaves the gun with Clarence to make it look like a murder-suicide.

Part four (Black Disc)
The Doctor takes Stewart and Reed forward to Christmas Day 3090, but history has now changed. Choosing to believe Clarence was a Slithergee agent, Mitchell declared war on the Slithergees in retribution. The war left Puxatornee a toxic wasteland, with starving humans eking out a miserable existence under martial law.

Mel and the Doctor are arrested as "enemy agents" by officer Potter. He is tricked into handing over his prisoners to the rebel Stewart and Reed, who pretend to be Potter's superiors, Lieutenant Stewart and Reed.

The dissidents are horrified. This is not the future they wanted. They demand the Doctor take them back to the previous night, Christmas Eve 3090, so as to stop themselves before they embark on their quest to kill Bailey. The Doctor drops them off on the previous night as requested, but it's the new, postwar timeline. The rebels wander off and become lost.

The Doctor and Mel, meanwhile, run into all the security agents again— for the first time, from the POV of Officers Potter, Stewart and Reed. In order to preserve history, the Doctor and Mel confess that they are Slithergee spies, since they know Potter will arrest them as such tomorrow morning.

Mel points out that there must be another Doctor and Mel in this timeline, and the Doctor realises they need to dematerialise before their counterparts arrive. Having secured the Leptonite crystals they need, they rush back to their TARDIS and leave, trusting that the alternate Mel and Doctor will sort out Puxatornee.

Cast

 * The Doctor - Sylvester McCoy
 * Melanie Bush - Bonnie Langford
 * Mitchell - Richard Gibson
 * Bailey - Pamela Miles
 * Stuart - Francis Magee
 * Reed - Audrey Schoellhammer
 * Potter - Trevor Littledale
 * Professor Capra - Trevor Martin
 * Slithergee / Clarence - Daniel Hogarth
 * Security Guard - David Darlington

Continuity

 * The Doctor first encountered the Quarks on Dulkis in the company of Jamie McCrimmon and Zoe Heriot during his second incarnation. (TV: The Dominators)
 * The musical group Pakafroon Wabster is mentioned for the first time in this story. They would be mentioned in a few more stories before making an actual appearance in COMIC: Interstellar Overdrive.