Onboard the Dalek craft Davros is placed in a cell. He tries to speak with two of the Daleks guarding him, who explain he is going to face trial on their home planet. He tries to persuade them that they must not turn against their creator but they disregard his remarks and override his life support unit, leaving him immobile in his cell.

Down in the bowels of the ship two creatures named Guz and Raz discuss the recent capture of Davros – pondering whether his treatment is justified considering he is the creator of those holding him. They assume such instances are typical of Dalek behaviour and wander off to another part of their ship.

In her ship, Lareen receives another message from Alydon, who reminds her that she is in stealth mode to evade being detected by the Daleks – but this will only last whilst the ship has power. He orders her to dock with the Dalek ship, don the ‘stealth suit’ provided for her and carry out her mission – which she will have just three days to complete before the power runs out and she will be detected. He asks her to keep reporting back on her progress then signs off.

On the Dalek ship Davros sits in his cell, infuriated at the treatment he has endured. He claims the Daleks are misguided for not recognising the Doctor when they landed on Necros, but assures himself that he will convince them to follow him and resume his place as their leader.

Monitoring Davros via a security system, the Daleks note that he is talking to himself. They reveal they have orders to keep him conscious so that he can contemplate the crimes they are soon to prosecute him for then order that a nutrition machine be linked to his life support system.

Below deck Guz and Raz set about their work – sucking the fuel residue from the engines. Despite disliking the job they face extermination for not complying with Dalek orders, and eventually they finish. As they clean themselves off they see a ship approaching outside from a observation portal, and puzzle why the Daleks have not destroyed it.

Lareen docks with the Dalek ship and waits to see if she has been detected. Satisfied she has evaded security scanners she puts on her stealth suit and activates it – causing her to become invisible and therefore undetectable. She readies herself and then leaves, eventually arriving in one of the fuel vents.

Guz and Raz arrive in Davros’ cell and assist in connecting the nutrition tank to his wheelchair. The captive scientist claims he does not need the device but the Dalek supervising the installation tells him it is the will of the Supreme Dalek that it be connected. Davros examines the twos slaves working beside him and the Dalek explains that they are Graalians – mollusc like creatures that consume the fuel residue in the engines to prevent it corroding the hull. Davros again tries to entice the Dalek into identifying him and acknowledging his authority but he fails, and is left alone once more.

Lareen continues her trip through the fuel lines and emerges in a more open where she is greeted by Guz and Raz, who can see her despite her stealth suit. They do not seemed alarmed by her presence; instead they suck the fuel residue covering her so that she is clean and dry. They then introduce themselves and ask why she is onboard the ship, assuming her to be an assassin for Davros. Lareen doesn’t confirm their suspicions; instead she asks the two creatures why they are onboard. They claim they are simply there to die – the Daleks have placed something in the fuel that makes them both addicted and dependent on it, but it is slowly killing them at the same time.

A Dalek enters and tells the slaves that they are required elsewhere. They promise they will go to their work soon and the Dalek leaves. Guz and Raz turn to Lareen and ask why the Daleks did not detect her – which she claims is the result of her stealth suit. She asks them if they will help her get to Davros, which they agree to. They do, however, ponder why Lareen is going to kill Davros (which they still assume is her intention) when it is likely the Daleks will do so following his trial. The young Thal claims she cannot explain what her intentions are because her mission is secret, and reluctantly the two Graalians end their questioning and lead the way to Davros’ cell.

On the bridge the Daleks discuss the status of their prisoner and his attempt to ‘make contact’ with his creations. Elsewhere in the ship Lareen arrives outside Davros’ cell and bids her two guides farewell. They depart and she resumes her work – managing to gain entry to the cell by using a short-range teleport. The machine is detected by the Daleks and they hurry to find what has caused the disturbance – believing Davros to be responsible.

When they arrive they order him to surrender the device that caused the energy discharge – claiming he has something hidden from them. He rubbishes their claims and upon scanning the room they are forced to admit there is no device in the cell. They leave Davros once more but this time he is not alone – Lareen has remained inside, undetected. She whispers to him and he tries to see who is talking to him – but he doesn’t see her because of her stealth suit.

She identifies herself as a Thal and he ponders how she got onboard. He begins to suspect the voice he hears is in his head and she laughs, but doesn’t drop the idea. She asks if he assumes her to be a voice he recalls from memory of if she is an invention of his mind that is going to help him rationalise what is going on – in which case he may well be slipping into madness.

Davros ignores her, hoping he will take back control of his mind in doing so. She claims she has arrived to give him a proper trial for his actions against the universe and tells him he should be grateful for the opportunity to face a less biased jury. Slowly Davros begins to accept that Lareen exists but warns her that the Daleks will eventually catch her and calls out to them, warning that there in an intruder in his cell.

After a few moments a Dalek enters and asks where the intruder is, but Davros is forced to admit that he does not know. The Dalek tells him that it cannot see anything else in the cell and this drives Davros to anger, the uncertainty of his companion’s true form evades him.

Having left when the Dalek opened the cell door, Lareen arrives back on her ship and transmits her mission log back to Alydon. She questions whether Davros’ anger is born from fear or insanity and claims that if he wishes to know the truth about why he cannot see her he will be willing to listen the next time she returns to his cell – which will be the following day. She also questions if she can trust Guz and Raz, and decides she must be cautious for they may be Dalek agents. Finally Lareen notes that the ship will go undetected for a much shorter period of time that she will – therefore her planned method of escape must be abandoned.

The next day, as Guz and Raz continue their fuel-guzzling duties, Lareen returns to fuel line and wonders how she will return to Davros’ cell, the teleport having proven too dangerous. She asks the two Graalians to help her gain access to the cell again and although they are concerned Lareen might expose them as traitors if she is caught by the Daleks, they do agree to help and reveal that they have manufactured another way of getting into Davros’ cell by gnawing through a section of fuel piping.

She manages to make her way inside the small room and, upon hearing her entering Davros calls out, asking who is there. The Daleks see this and again note that their creator is growing irrational. They also notice that part of the cell has been damaged and order that it be repaired…

In his cell Davros speaks to Lareen again – claiming he can hear her move around the room. He still cannot see her but he claims she does exist, telling her that when the Daleks see how she has entered they will arrive to repair the damage and at that point she will be detected. Lareen claims she can evade Dalek scanners and that is why Davros cannot see her – for he has become no more that one of his own creations.

The two discuss the Daleks and Davros claims he is far more than any other Dalek. Lareen identifies his wish to be an authority over his creations but instead they have abducted him – something Davros claims is arrogance. Lareen proposes that such arrogance is inherited from their creator but he dismisses the notion. For a split second Davros is able to see Lareen and she theorises that maybe he is more that just a Dalek after all, for it is only Daleks who are unable to see her. Again Davros asks why Lareen has come to his cell and she finally reveals why – she has come to save him. Davros is amused by this claim and descends into a maniacal fit of laughing. A group of Daleks enter and order him to be silent. He realises that by opening the door they have let his visitor escape, and brands them fools for doing so.

Once again Lareen returns to her ship and makes a report to Alydon, noting Davros’ reluctance to listen to her. She realises that her mission has become more important than her own life then explains that her ship will be detectable by the end of the solar day. She plans to leave the ship and jettison it by remote control, herself remaining hidden thanks to her stealth suit.

On the third day Guz and Raz arrive in Davros’ cell to remove the nutrition tank. As they work they notice another machine suspended from the ceiling and then the leave. The Daleks guarding Davros reveal that it is a restraining device and sure enough it grabs onto his body and lifts him from his chair so that he is rendered immobile. The Daleks explain that to stop his apparent delusions they will occupy his mind with the pain of living without his wheelchair. Eventually he will slip into a vegetative state and they will awaken him when required to do so for his trial on Skaro.

The Daleks leave him to his diminishing thoughts and Davros vows not to let the pain affect him. He claims the Daleks will not be able to get rid of him then stops speaking when he realises Lareen has returned to his cell – for another split second he sees her. Removed from his life support system he is able to suffer as the victims of the Daleks have – Lareen claims he is reverting to a point in his life before his body and mind were invaded by Dalek thoughts. Davros concedes she is almost right – something has changed in him but not as she interprets it. Lareen tells him there may be hope for him yet.

Receiving orders from the Supreme Dalek the Daleks in the ship shut down surveillance in Davros’ cell so that they cannot be conditioned by his ranting. They announce that in two solar days they will arrive on Skaro, and their creator will answer or his crimes.

Lareen tells Davros that nobody is listening to him but he insists his Daleks will eventually and he will help them advance. She tells him that is his ego talking – the same ego that caused his downfall. She claims he has two choices left – either listen to her or surrender to agony.

Davros refutes the claim that his ego has corrupted him; instead he says that it is the drive for his ambition. Lareen continues to belittle him, claiming that the Daleks want to get rid of him because they are tired of his superiority complex. As the two talk Davros is finally able to see Lareen properly – and takes the chance to pour scorn on her and her people – claiming they have advanced no further from the weak beings he determined to destroy many years ago. Lareen claims that the fact he can see her is because he sees himself as more than a Dalek – his ego has struck again.

Lareen reveals the options she has been given to deal with Davros. Either she can be his assassin or his enlightenment and freedom. He does not believe that she has come to rescue him but Lareen tries to convince him that there is hope for him – by seeing himself as more than a Dalek he has proved he can change, and this change is something she believes can be introduce to the Daleks so that their reasoning is not so rigid as his once was. She pleads for him to let go of the bitterness he has harboured in the past and instead use his great intellect to help the universe change for the better. Davros asks Lareen if she has finished and she claims that she still has one thing left to do. She takes a small object from her person and shows it to him…

In the fuel lines Guz and Raz detect a change of course in the ship – they are almost back on Skaro. They ponder if Lareen has killed Davros yet and decide to go and check the cell to see how she has progressed. Now the have nothing to lose.

Davros identifies the object in Lareen’s hand as a capsule of the Movellan virus, concentrated to a form capable of wiping out the Daleks. He comments that the Thals, once peace-loving people, have turned to genocide and Lareen claims it is essential for the well being of the universe. He asks why Lareen cannot release the virus herself when they arrive on Skaro but she persists, offering him the chance to redeem himself. At last he seems enticed by this opportunity, the power he would wield could make him whole again…

Soon the ship lands on Skaro and Davros asks Lareen to stand by his side when he releases the virus in the Dalek city. Suddenly Guz and Raz arrive, infuriated that Davros is not dead yet. They mock the incapacitated scientist and move to harm him, and then turn on Lareen for wanting to convince him that he had a good side.

Before they can act the Daleks arrive and order them to stand back. They protest that the Daleks will kill Davros anyway, but then realise that there is a chance they will opt out as Lareen did. Before they can do anything more the Daleks exterminate them and place Davros back in his chair.

Soon they have brought him into the Dalek city, where the Supreme Dalek is waiting to begin the trial. He reveals that soon he is to be upgraded to the position of Dalek Emperor, but Davros must be exterminated first.

Davros is brought in, with the invisible Lareen still by his side. He asks what charges are being brought against him and thy accuse him of betraying them to create ‘impure’ Daleks. Lareen tells Davros to release the virus and he holds up the capsule so that the Daleks can see it. The Supreme Dalek orders him to be killed but he warns that if he dies the virus will be released.

In a bid to regain Dalek trust he reveals that a Thal spy is standing beside him, wearing a stealth suit that shields her from being detected. The Daleks open fire but Lareen manages to escape before they can hit her. Davros takes the opportunity to reason with the Daleks – claiming that he deserves to be their leader because he has saved them from the destruction threatened by Lareen. After a few moments the Daleks are on his side – Davros is victorious again.

Lareen runs or her life across the city, the Daleks close on her tail. With the power of her stealth suit almost gone she makes a final report – explaining that Davros has betrayed her and she will soon be killed. She claims that she has seen into the mind of Davros and made him understand her – in his heart he knows what he is doing is wrong, and this doubt will serve to destroy the Daleks in the future, for buried in the mind of every Dalek is the knowledge that they are inferior.

As her suit shuts down Lareen uses the last of her power reserves to transmit the final report to Alydon, and then is found by the Daleks. They take her to Davros, who laughs at her desperate situation and thanks her for the redemption he has achieved. Lareen claims the Daleks will never truly trust him, even though they now wish to make him Emperor. Davros claims she is mistaken and she admits she has been of many things.