She practically ran back towards the laboratory but stopped short when she heard gunfire. Close. Her breath caught in her throat and she pressed herself back against the wall. They were coming this way.
Another burst of gunfire and she felt the minds flick out.
She checked for anyone else approaching her, but finding it quiet made her way along the corridor until she reached the passage where she had heard the fighting. A little way down, five or six metres, were two of the Palace Guard, sprawled on the floor and quite dead.
Leto approached them cautiously, searched the bodies and took a pistol and knife from one. Then she cut the comms bracelet from the other; if the security code could be cracked then she could find out what was going on.
She ran back to the laboratory, but met no-one else on her way there. Inside, the Master was still working, though to Leto's unskilled eye the work looked almost complete.
"Something's happened," she said.
"Oh?" He didn't look up and the tone was dangerously mild.
"There was gunfire on the floor above. Two of the Palace Guard shot dead. And the palace is quiet."
"You seemed to have acquired some equipment." He was looking at the pistol, then his eyes fell on the comm bracelet. "Give me that."
He examined the bracelet and then quickly made some adjustments to the control before holding it to his ear. After a moment he frowned. "It seems you're right. Casta has taken a somewhat direct route to achieve her goals, no doubt the Doctor's influence; there's a civilian revolt across the city. The Guard have been called out to deal with them."
"But I saw men shot in the palace."
"I doubt that Peron is much of a general. He'll have left the palace exposed." He sighed and seemed to come to a decision. "All right, Leto, there isn't much left to do here. Lock the doors and check the power distribution. Even with this disruption I should still be able to get enough power from the main grid." He glanced at the Doctor through the window. "And when you're finished, bring them out here."
The laboratory was easily sealed, indeed it was designed so it could be cut off quite easily from the rest of the building. Even with explosives, it would take some time for any rebels to get through the main doors.
Leto turned to the wall entrance that led through the passageways between the halls, wondering what arrangements had been made for sealing that, when a figure burst through the panel and into the lab. He was in such a rush that he almost tripped, but in a remarkable demonstration of agility managed to regain his footing.
The Master turned to the new arrival. "Ah, King Peron, and what, may I ask, is the rush?"
"It is finished, is it not? It must be finished!"
"I'm afraid not. There are a few more adjustments to make," said the Master, raising an eyebrow.
"I will cast you down! I must ascend at once, this cannot wait." He glanced over his shoulder. Eyes widening at the sight of the open wall panel. "They have betrayed me. I have been betrayed!"
The Master cocked his head to one side. "Yes, I'm afraid you have. Leto?" He spoke quietly enough for Peron not to pay attention, not until Leto lifted the pistol and aimed it at his chest.
But before he could do anything, she shot him.
"Well, that takes care of that," said the Master. "Is there a way to seal that panel?"
"Not that I know of. But given how paranoid Peron was I'm not sure anyone else in the palace knows about those passages."
"Well, do keep an eye on it and feel free to let me know if a band of rebels are charging towards us. I've almost finished here."
In the next few minutes Leto felt no less than three explosions rock through the building. She closed her eyes and tried to find out how far away these rebels were; inside the palace, certainly and somewhere in this wing, but with the sprawling building as big as a town that didn't necessarily mean they were in immediate danger.
Her eyes flew open. "They're close. On the central stairway for this wing."
"Are they coming here?" snapped the Master.
"I don't know. But Casta, she knows about this. Surely she'll wish to stop it?"
"Get them out here." He stabbed at the Doctor with one finger.
Leto deactivated the seals on the isoward and, with her pistol, invited the Doctor and Jo to join her in the main laboratory. As the Doctor passed her, he said, "Even if he does succeed, what do you think will happen to you?"
"You seem to be under the mistaken impression that I care," she said, almost under her breath.
"Well, Doctor, it seems it is finally time to say goodbye." The Master nodded to Leto to switch on the power, watched the dial begin to tick up. "What? Nothing to say? No last minute appeals filled with your usual sentimental nonsense."
The Doctor gave him a stony stare. "What would be the point? You never listen."
The Master clapped his hands. "Ah, finally you learn."
"They're here," said Leto, with a glance at the doors.
"How long?" asked the Master.
Leto checked the power readings. "Forty-five seconds." She glanced at the artefacts, frowning as she felt something at the back of her mind. "Are they alive?"
"In a manner of speaking. The technology is partly organic."
Leto pressed one hand to her temple. "I can feel them. It..."
She cried out, clutching her head in her hands; the whine of power increased and Leto fell to the floor and did not move. The Master scooped up her pistol and swung it around to the Doctor before he could move.
"I don't think so, Doctor."
"Is she alive?"
"Irrelevant. In a matter of moments it will be my choice who lives and who dies. And I can assure you that you will be quite dead." He held the gun steady, watching them as he backed away towards the neural network. "Goodbye, Doctor."
So intent was the Master on making sure the Doctor did nothing foolish at the last moment that he did not notice Peron move. "I am king," he murmured, though no-one heard. He clawed the ground, then manage to steady himself and stood up shakily. "Usurper!" he cried. "It is my destiny!"
He threw himself at the Master, knocking him to one side and leapt into the machine, into the neural net.
The power reached critical. The lights dimmed as the artefacts took all the energy they needed from the grid.
Dark.
Then a blinding flash of light.
And the sound of gunfire just outside the main doors. A shout to open up.
The Master stood up, gun still in hand, to see the Doctor crouched over the neural network. "Get away from there."
The Doctor put up his hands and stepped back. "Looks like you had a lucky escape." His eyes fell on what now occupied the space where Peron had stood: a small stone statuette, the likeness to Peron was startling.
"No." The Master shook his head. "Impossible."
"The artefacts were a trap. A trap to catch the most intelligent and dangerous of criminals. And you fell right into it." The smugness in the Doctor's voice was unmistakeable.
"Well, Doctor, it seems you have deprived me of my prize, but I still have you. And I still intend to kill you." His threat was punctuated by another burst of gunfire from outside the doors.
"Looks like you've run out of time. You kill me and there won't be anybody to stop Casta's people from tearing you apart."
"I still have time to pull the trigger and escape."
"And what about Leto? If I'm dead then so is she."
The Master gritted his teeth and bit back the retort on his tongue. He looked down at her: still, but breathing. There was no way he could escape quickly enough with her when she was unconscious.
There would be, he considered, many more opportunities to kill the Doctor - and this would hardly be the most satisfying moment for that particular pleasure - but good servants were so very hard to find.