Alison needed no encouragement. With a balletic twist she dropped back down the hatchway out of sight, even while the dark mass of fully two dozen of the vampiric creatures surged forward like an avalanche. The Doctor raised his lantern high and hurled it shattering down onto the ship's hull, sending the hideous things leaping back with screams of rage and frustration at the rush of orange flame from the blazing oil. With liquid fire flowing about his feet he jumped down the hole after her.
The sole illumination was the fast dimming light of the flames above. Alison felt the Doctor's hands on her shoulders and she was propelled at unhesitating speed down the corridor into the impenetrable blackness of the ship's interior.
"Back to the power core," came his sharp voice in her ear.
"What? But the radiation..."
"One problem at a time."
The blue light of the core shone as a beacon when they rounded the corner and they piled into the brightly glowing surroundings of the power core chamber. While the Doctor hunched tensely over a bank of flashing dials Alison snatched up a chair and stood guard at the entrance. The crazed hissing and thunder of fast moving feet swept closer until the first of the creatures hurtled into view in the doorway, crashing down to the floor in a tangle of limbs when the desperately flung chair struck it head on. The door slammed shut, cutting off from view the enraged, contorted faces of its fellows. Their fists drummed uselessly against the metal.
"Phew," the Doctor remarked, a thread of strain running through his clipped calm. "That was a close one." He straightened, his fingers still resting thoughtfully on the controls.
"It still is." Alison stared up at the dazzling blue column of the power core. "How long do we have before that thing turns us into something no different from those creatures we just locked out?"
"Don't know. Can't be long. Apparently when they dragged George Carstairs down here he changed before they had time to bleed him to death."
The Doctor operated a control and the black metal sheath slid back over the core, leaving the room sunk once more into darkness but for the glow of the instrument panels.
"That should slow it down a little."
Alison fretted, darting back over to the door, where at least the creatures outside seemed to have abandoned their noisy attempt to batter their way in.
"We have to get out of here. The thought of even starting to... to change into..."
A wormlike chill of horror curled its way around her innards at the idea and even the Doctor paused, fingertips spread out on the console.
"I know, I know. But maybe I can shut the core down from here, or at least reprogram it so the emissions aren't so dangerous."
He didn't look too confident, and he didn't dive into the task straight away. A bad sign, she knew. But in an experimental manner he began to tap at a set of keys and brought streams of data flowing across a viewscreen. After a few seconds Alison heard his breath being slowly sucked back over his teeth.
"Oh, God. You sound like a plumber about to tell me it's a big job and it's going to cost me."
He moved on to a second set of keys and started tapping away again. His brow set into stiff lines, his lips tightened.
"Something's wrong," he said flatly.
He didn't respond to her sickly attempt at humour and she thought he was ignoring her. But when he moved on to a third panel he started talking again, either in reply or just continuing his own running commentary.
"A radiation leak from this reactor could be dangerous, but there's no way it could cause the kind of mutations we've seen here."
"But you said it had."
Alison sighed wearily.
"This is no accident, the output has been deliberately reconfigured to bring about this specific effect on living tissue." He jammed his knuckles against his forehead as if trying to massage his brain. "Why would anyone do something like that? And how? The knowledge, the technology required would be absolutely..." He shook his head agitatedly and moved on to yet another panel. "Just a minute."
Helpless to contribute, Alison made herself keep still and wait while he bent closer and closer to the screen till his brow was almost touching it. Then he closed his eyes as if in despair.
"What's the matter?"
"It's all here," he said softly. "Neatly logged in the computer, not that it did the crew of this ship any good. A clever piece of work. The power core was reprogrammed by a data stream projected down a focussed energy tunnel."
"But projected from where?"
"The energy signature's as individual as a fingerprint. It's my Tardis."
"What? But that's ridiculous. You're not saying you did this?"
His head swung towards her. His eyes were wide and honestly, deeply afraid, and the realisation hit her.
Jenny had been made welcome aboard the Tardis.
"Shan't keep you waiting long, my dear," the Master said smoothly, holding up to the light the plastic packet she had brought him. "Though I could have wished for a more substantial specimen for analysis. Still, I live to serve."
Jenny sat upright on the hard wooden chair to which he had directed her, knees pressed close together. A natural deference to his lordly manner led her to speak only when spoken to, and since the difference in size between the interior and exterior of this structure hadn't been mentioned she was ignoring it, and assuming all was as it should be.
"Yes, sir. Miss Alison said you were a very expert scientist."
"Well, I'm flattered to hear that. What else did she tell you about me? Nothing to alarm you, I trust?"
"Oh, no, she said you were harmless."
The Master stilled momentarily before the slow smile gathered on his face and his dark, shining eyes turned upon her.
"Ah, how right she was."
The Doctor and Alison looked up sharply at a metallic rattle from above their heads. Some fast-scuttling thing was moving about on top of the flimsy plates which formed the ceiling. They could see them bending and shifting under the creature's slight weight.
"We really need to get out of here," he murmured.
"As if we needed another reason."
"Quite." He turned quickly back to the controls and swept his eyes across the vast expanse of instruments. He tapped his fingers together agitatedly. "But I... I wasn't prepared for... I'm just not sure..."
"Hey." She placed a hand gently on his shoulder. "Come on, Doctor, you'll think us out of this like always. Just try to stay calm."
"What?" He rounded on her cattily. "Don't tell me to..." He stopped, held his breath for a second, and raised his hands. "All right. You're right."
"How could the Master be behind this anyway?" she asked. "I thought you programmed barriers into his mind so he couldn't hurt anyone."
"I did. But whatever's programmed can be reprogrammed."
"But didn't you say it was impossible for him to reprogram his own mind?"
"It is." He frowned. "I'm sure it is." The eyes that met her gaze were pained with worry. "There are very few beings in the universe I'm willing to admit might be able to think of something I didn't. But this is the Master. And he's had years."
He returned to the controls, shoulders tensely hunched, and she tried to come up with some words of encouragement.
"Well, at least if it comes to a showdown you can just use your little remote control thing and turn him off. Easy win."
"That's not the point." He had gone back to tapping slowly at the keys. "I'm the one who preserved his life. I knew what he was, but I still saved him even when he'd resigned himself to death. That makes everything he does for the rest of his existence my responsibility. Anyone who dies here, it's as if I killed them myself."
She knew she should leave him alone, to work on a way out, but the haunted darkness of his tone had her pitching in again.
"Well, who knows? Maybe we're leaping to conclusions. Maybe there's some explanation for all this that we're not seeing."
"Let's hope so."
The Master's soundless footfalls carried him back to the console where Jenny awaited him.
"Ah, thank you for your patience, young woman. My work is reaching a crucial stage and I wonder if I could beg your assistance?"
"Of course, sir." She stood. "What would you like me to do?"
"Well, I'd like you to look over there."
She followed his pointing finger and turned her back on him. The next second a reeking pad of cloth was clamped over her nose and mouth and a bright blade flashed before her wide, horrified eyes.
Jenny's blood spattered the shining steel.