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The Mutant Phase was the fifteenth story in Big Finish's main range. It was written by Nicholas Briggs and featured Peter Davison as the Fifth Doctor and Sarah Sutton as Nyssa.

It was the third of the Dalek Empire semi-linked stories and was an early example of a non-original piece of Doctor Who fiction published by Big Finish. It was in fact a remake of an unlicensed audio drama published by Audio Visuals.

This was, according to the fictional timeline, the first performed story to feature an encounter between either the Fifth Doctor or Nyssa and the Daleks.

Publisher's summary[]

In the 22nd century, the Daleks have occupied planet Earth. By the 43rd century, only a handful of humans survive. Still further into the distant future, a Thal scientist must choose whether to betray his heritage, or see the universe destroyed.

When the Doctor and Nyssa find themselves trapped in this deadly chain of events, they must decide who their real enemies are. What is certain, however, is that no matter where the Doctor turns... his arch enemies, the Daleks, will be waiting for him.

What could possibly be worse than that? The Mutant Phase...


Episode one[]

On the starship Dyoni, Professor Ptolem completes his audio survey log. An odd echo is heard as he speaks. The ship is sweeping the trade routes and Ptolem reports that every planet they have surveyed is devoid of life. He determines that some force or thing has destroyed everything. He thinks it must be some kind of natural disaster that caused all this.

As he tries to come up with a solution, he is interrupted by Commander Ganatus who tells him they've picked up something on the long range scanners. The scanners have picked up a life form heading straight for them at incredible speed, three times their maximum. The life form turns out to be a group of over 100,000,000,000 units making up the whole, flying in close formation. Ganatus decides it's a swarm.

The ship decides to get out of the area but they realise that swarm will overtake them. They cut off the engines and divert all power to their defence screens, hoping for the best. The swarm hits them and the ship is caught in the wake, flying out of control. When the ship is finally freed, the swarm has vanished. Ganatus realises that they are in space around Skaro.

Nyssa is making repairs on the TARDIS audio systems for the proximity alarm to avoid a problem like they had when she and the Fifth Doctor visited Alaska. The alarm goes off and the TARDIS is thrown into a Time corridor. They realise they are being drawn towards the end of it. The TARDIS isn't able to break free but they can bounce off it.

The land roughly in a large cornfield. The Doctor says he has no idea where they are, as the time corridor interfered with the TARDIS systems. Nyssa notices a large number of wasps buzzing around them. Nyssa gets stung in the arm by one of them. She insists she's fine, but the Doctor looks at it anyway. Suddenly, they hear a loud whoosh and a blur overhead. Nyssa thinks that's a sign of some kind of civilisation. The Doctor decides they should explore and eventually, they'll come out of the field.

Now on planet Earth, Ptolem contacts Ganatus through a communicator. Weather conditions are making the transmission difficult. Ptolem is trying to get back to their base but is over the human's bunker. Ptolem wonders if they saw him, but Ganatus isn't worried.

In an underground bunker, Albert is on a pile of books looking through a periscope. Delores asks if he's found anything. He did see someone stumbling around but then disappear in the storm. Delores asks Albert if he is going to help them. Albert replies that they have with food and medical supplies. Delores is concerned that if the aliens blast off again, they won't have any more food or supplies. Albert says they'll face each situation as it comes. She insults him and leaves.

Nyssa and the Doctor continue to walk through the field. Another spaceship passes overhead. They decide to walk in that direction. Suddenly, they hear gunfire and grenades. They decide to head back towards the TARDIS.

Ptolem arrives at their base, bringing back more soil samples. Ganatus laughs, telling Ptolem that the Doctor has finally been spotted on the time track.

The Doctor and Nyssa crouch down in the field, lost and unable to find the TARDIS. The Doctor wishes he'd brought his tracker. They try to get their bearings. Nyssa finds a body lying in the field. After some investigation, they determine that he was an American sheriff from the state of Kansas. Nyssa notices that he has scars on his head and bullet hole in his back. The Doctor looks for a warrant card and using the date of the card (2139), is able to determine the year. He tells Nyssa that the scars on the sheriff's head are from alien technology which was grafted right on to his skull. The Doctor goes on to say that he was under the control of an alien intelligence and was shot in the back and the technology removed from him. He tells her that they are on Earth in 2157 and they have to find the TARDIS.

Ptolem activates the time track and determines that the Doctor is in 2158. Ptolem has read the Doctor's history and knows he won't be staying there long.

The Doctor and Nyssa are moving quickly through the field, trying to avoid any gunfire and find the TARDIS. They hear a shotgun being cocked and a voice telling them not to move. Nyssa notices that this man is another sheriff, the Doctor adding that this one comes with alien technology. The Sheriff asks if they are with the other freedom fighters. The Doctor says no, but they are hiding in the "blue box over there". The Sheriff doesn't believe him and contacts control to report their capture. Nyssa sees that the wasps sting him and he doesn't seem to notice. The sheriff requests backup. A spaceship lands nearby. Nyssa asks the Doctor what it is. A battle-damaged Dalek comes over to them demanding they identify themselves and then determines that they have escaped from the work camps. The Doctor tells Nyssa to get ready to run to the TARDIS and the Dalek demands to know what a TARDIS is. They run to the TARDIS, being fired on by the sheriff and the Dalek. The TARDIS dematerialises and the Doctor explains to Nyssa that he's met the Daleks before, but they haven't met him yet. Nyssa is complaining that the sting from the wasp is hurting her arm again. As she goes for the medical kit, the Doctor realises that by dematerialising, they are back in the time corridor again.

Ptolem tells Ganatus to check and confirm that the Doctor is back in the time corridor and is in transit.

Nyssa is unable to set the controls and can't get the destination to register. She says it's a shame that the Doctor can't do his bouncing trick with the corridor again. The Doctor says that it doesn't matter, wherever they land there are sure to be Daleks there.

Ganatus says that the Doctor's arrival is imminent. Ptolem says they'd better meet him. Ganatus says that they really don't have a choice.

The Doctor tells Nyssa that they are falling into a trap set by the Daleks. Nyssa says that they should put up a fight to put some space between them and the Daleks. The Doctor tries to dematerialise to put them in a different place than they're supposed to be.

Ganatus says that the time corridor has been activated and Ptolem asks him if he ever wonders why they're doing this. He says that they're doing what has to be done. The time corridor stops and a Dalek exits asking for a report. Ptolem tells the Dalek that the Doctor will be arriving soon. The Dalek says that the Doctor will soon be in their power.

The Doctor asks Nyssa if there is any change in the special coordinates but she is unable to tell from the instruments. The Doctor decides to risk it and materialises.

Delores tells Albert that it was lucky that the Thals showed up and wonders if they do this kind of thing all the time. They hear the TARDIS materialising and decide to go investigate. Albert thinks it might be the Thals again.

The Doctor and Nyssa exit the TARDIS and find that they appear to have materialised inside a structure. They don't see any Daleks and decide to go investigate.

The Daleks return and ask Ganatus where the Doctor is, as the time track says he should have arrived. Another Dalek reports that the TARDIS did arrive at the right time, but he has altered the coordinates. The first Dalek asks if the TARDIS can be found. They say that the Doctor is somewhere on the planet and they will begin a search.

The Doctor and Nyssa realise they are underground and the structure is under tremendous pressure causing cracks in the floor and walls. They decide that they have to find another way out, since if they dematerialise, they'll wind up back in the time corridor. Nyssa hears footsteps coming towards them and wonders if it is more Robomen. The Doctor tells her that the Dalek invasion of Earth was foiled in 2167. Delores finds the Doctor and Nyssa and mentions to Albert that they aren't Thals. The Doctor asks if they said "Thals".

The Daleks decide to open the time corridor and return to Skaro. One of the Daleks begins speaking oddly and has trouble controlling itself. Its casing cracks and the other Daleks begin screaming about the Mutant Phase and, seeing that the Dalek is infected, decide that it should be exterminated. Ptolem pleads with the Dalek that the infected Dalek should be examined. The Daleks try to kill it as Ptolem and Ganatus watch the creature grow and mutate.

Episode two[]

Ptolem takes the mutant creature from the Dalek casing. He wants to study it at the larva stage. The Dalek states that now that the Doctor has been captured, Ptolem's research is of no importance. Ptolem tells the Dalek that the Doctor isn't captured yet and he was granted full authority to do what is necessary to get rid of the Mutant Phase.

Albert tells the Doctor and Nyssa that the Thals have been helping the humans. When asked about the Daleks, neither Albert nor Delores knows anything about them. Albert asks if they're friends of the Thals. The Doctor asks for an explanation of what's been happening on Earth. Delores says there was a global disaster about 30 years ago. Delores' mother was one of the survivors. Nyssa asks what caused the disaster. Delores and Albert decide to take the Doctor to see Professor Karl Hendryk, saying he's the only one who understands what happened. Albert notices Nyssa's arm. They decide to have Albert look at the arm while Delores takes the Doctor to see Karl.

Ganatus tells Ptolem that the creature is secure in a containment field. They discuss what will happen to them if they can find a cure, Ganatus thinking they will probably be exterminated. Ptolem says that he has an "insurance plan" but before he's able to tell Ganatus about it he notices the creature dying. They feed it some nutrients and it immediately begins to improve. They have the defence screen power increased, saying they're going to see marked improvement very quickly. Ptolem leaves to go back to sleep. Ganatus watches the creature.

The Doctor asks Delores how many survivors are in the caves, she tells him about 20-25 people. She tells the Doctor that there aren't any other groups of survivors, as the Thals did a planetary sweep and were surprised to find them. Delores says that she doesn't hold much hope for the human race. Karl told her there are other humans out there, but if they're there why haven't they come to help?

Albert takes Nyssa to a room to work on her arm. He gets the medicine box. He begins to act oddly and politely excuses himself. Nyssa sighs and works on the wasp sting on her own.

Dolores takes the Doctor to Karl's room. He enters a dark room, calling out for anyone. Trying to find a light switch, the Doctor is told that there is no light. Karl invites the Doctor into the room to sit down.

Nyssa notices the sting is getting worse. She finishes and goes looking for Albert. She hears him talking to someone, mentioning the TARDIS.

Karl asks if the Doctor is a Thal, but decides he's not when the Doctor begins asking questions about what happened. He tells Karl that he's been brought here by the Daleks and asks if he's ever heard of them. Karl remembers something about a war with them. The Doctor wonders if the Daleks are responsible for what happened on Earth, but Karl tells him that this is not the case and asks the Doctor to describe the Daleks to him. Karl says it was not the Daleks who caused the destruction of Earth. He says he wants to show the Doctor something and takes him to another room.

Ganatus notices that the rate of growth of the creature is increasing. He says that it's also showing signs of the maturing process. The creature is moving out of the larva stage.

Karl takes the Doctor to a room and gives him a flashlight. In the room is one of the creatures, dead. The Doctor says it is insectoid and over 100 metres in length. Karl says to imagine hundreds of them flying across the sky. He says when they left, they sucked the life out of the planet taking all the minerals, nutrients and micro organisms out of the soil. He says that any defence was useless and they sucked up the destructive forces used against them. Karl tells the Doctor that they died suddenly. The Doctor asks how they died out but Karl doesn't know; one day they just started to die, there was nothing left to sustain them. The Doctor wonders what the connection is with these creatures and the Daleks.

A Dalek reports to the Dalek Supreme that the Mutant Phase on Skaro is increasing. Mutant creatures are assaulting the defence barriers. They continue to divert all power to the defences but collapse is imminent as they are absorbing energy from the defence barriers. A report comes in from the Daleks on Earth who tell the Dalek Supreme that the Doctor has been located. The Dalek Supreme demands that a time squad be dispatched to capture him.

Nyssa finds Delores, demanding to see the Doctor. Delores demands to see Albert. Nyssa tells Delores that she heard Albert in communication with the Daleks. Delores has no idea what she's talking about but takes her to see the Doctor.

An alarm sounds waking Ptolem up. Ganatus walks into his room, telling him the Daleks are here and that they've found the Doctor. The Daleks want Ptolem and Ganatus to be with the Dalek time squad.

Karl asks if he has answered the Doctor's questions. The Doctor wants to know why Karl doesn't trust the Thals, saying they are the most peace-loving creatures in the universe and sworn enemies of the Daleks. The Doctor determines that something is very wrong and not how it should be.

Heading down the hall, Delores says that Karl would have taken the Doctor to see the "monster". Enroute, they run into Albert. Nyssa is furious, asking who he was talking to, saying that she heard him telling someone about the Doctor and the TARDIS. Albert thinks there's been a misunderstanding. She demands that Albert get out of their way and he grabs her arm, keeping her there. Nyssa hits Albert, knocking him to the floor. Albert tells them that the Doctor and Nyssa must not be allowed to escape in the TARDIS. Delores has no idea what Albert is talking about. He demands that she obey him but Delores responds by punching him and they head back to find the Doctor.

Ganatus says that the creature is still growing. The Daleks tell them that the creature should be exterminated but Ptolem insists that it's a vital part of his work. The Dalek tells him that they must proceed to the bunker as that is where the Doctor is. Ganatus says the weather is too harsh for them to go and they must wait. The Dalek says he has orders to exterminate them if they do not obey. Ganatus tells Ptolem that it sounds like the Daleks mean it this time.

Nyssa finds the Doctor and tells him that they have to get back to the TARDIS. Delores tells the Doctor that Albert is acting weird and Nyssa thinks he's working for the Daleks. The Doctor agrees saying the only safe place for them is in the TARDIS. Nyssa sees the creature, asking what it is. The Doctor doesn't answer and they head back to the TARDIS.

The creature continues to grow and more power is diverted to the defence screen as it attempts to break through.

Ptolem and Ganatus continue walking through the storm heading towards the humans' bunker. Ptolem wonders how they found the Doctor and Ganatus says that, if they have found him, all their troubles will be over. Ptolem reluctantly agrees. The Dalek tells them to hurry.

Delores leads the group towards the TARDIS. The Doctor asks how Nyssa's arm is and she replies that it's getting worse. As they walk, the group comes upon a wall that wasn't there before. Delores is sure they are going in the right direction. The Doctor notices that it's not really a wall but a bulkhead door. Delores concludes that Albert must have activated it. Albert then walks in holding a gun and tells them to stand still. Delores wants to know what they're waiting for. The Doctor has a good guess as to what it is.

The Dalek squad arrive at the bunker. The Daleks go in first followed by Ptolem and Ganatus. The Dalek leader tells the others to activate heat scans to find the Doctor.

The Doctor asks Albert how the Daleks are controlling him. The Doctor continues to walk towards Albert, still questioning him. The Doctor says that if the Daleks had wanted him dead, Albert would have done it already. Albert fires his gun and Karl shoots Albert, grazing his scalp. Nyssa opens the bulkhead door and finds the TARDIS. The Doctor tells Nyssa to get inside and suggests that Karl and Delores do the same. The Daleks enter the base, firing their weapons. Karl returns fire and is exterminated. Albert tells Nyssa not to move and grabs her again. Delores punches Albert to get him to let go. The Doctor enters the TARDIS. The Daleks demand that he leave the TARDIS otherwise they will exterminate the women but the Doctor refuses. Ptolem and Ganatus show up and Ptolem then attempts to persuade the Doctor to leave the TARDIS. He asks for a chance to explain and is convinced that afterwards, the Doctor will help the Daleks. Ptolem tells him that he can't take off because of the time corridor. The Doctor demands that Nyssa and Delores be allowed to enter the TARDIS and then Ptolem can explain. The Daleks find that unacceptable and exterminate Delores. The Daleks threaten that if the Doctor doesn't surrender, they will exterminate Nyssa. The Doctor exits the TARDIS saying "I surrender".

Episode three[]

to be added

Episode four[]

to be added




  • The Daleks use Robomen as guards in 22nd century Kansas.
  • This is the first time that Nyssa has ever seen or heard of a Dalek.
  • The Daleks regularly extract DNA to facilitate operations at their reproduction plants.


  • Both the Thals and the Daleks count in Rels.
  • Nyssa compares wasps on Earth to Lime Grove Wasps on Traken.
  • In the alternative timeline, the Thals provide the survivors on Earth with food.


  • Nyssa has been repairing the TARDIS' proximity alarm.
  • The Doctor uses the HADS to move the TARDIS.

Theories and concepts[]

  • The TARDIS is caught up in a damaged spatial temporal causal nexus point.
  • Meeting or communicating with one's past or future self is against the First Law of Time.

Time travel[]


Cover gallery[]


The DWM preview for this story by Lee Sullivan.

External links[]