As the Doctor stormed into the Rotunda he snarled: "I'm going to need a packed lunch."
"Hang on." River commented as she dug in her bag, and she pulled out her diary in her search.
Teresa pulled away from the Doctor to comfort Donna, and he took the opportunity to kneel beside River and asked darkly: "What's in that book?"
"Spoilers." She replied curtly, and the Doctor asked with narrowed eyes: "Who are you?"
"Professor River Song, University of-" River began and the Doctor cut her off as he snapped: "To me. Who are you to me?"
She closed her eyes and sighed in irritation, and she muttered: "Again, spoilers."
"And Terry?" He demanded, and River just handed him the lunch, saying flatly: "Chicken and a bit of salad. Knock yourself out."
The Doctor stared at her for a moment longer before taking the lunch and saying loudly to the group: "Right, you lot. Let's all meet the Vashta Nerada."
He flipped his torch with one hand and Teresa sighed. The Doctor leapt to the side and lay down near the shadows, flashing his torch and pointing his sonic into it. He kept Teresa with him, not trusting the shadows and not trusting River. It made Teresa sigh internally- clearly her attempt to pacify him hadn't worked.
River and Donna were talking quietly, and they couldn't hear until Donna asked loudly: "What are you talking about? Are you just talking rubbish? Do you know them or don't you?"
"Donna!" The Doctor scolded. "Quiet, I'm working."
Teresa shot both Donna and River sympathetic glances, guessing what they were talking about.
"Sorry." Donna muttered, before she and River got back into a quiet conversation.
"Okay, got a live one." The Doctor suddenly called triumphantly, pulling back and keeping Teresa behind him and in the light. He turned to the group and explained: "That's not darkness down those tunnels. This is not a shadow. It's a swarm. A man eating swarm."
Teresa handed him the lunch and he knelt back down by the shadow. The Doctor picked up a chicken leg and threw it at the shadow, and by the time it hit the ground underneath the chair it was just bone left.
"The piranhas of the air." The Doctor murmured. "The Vashta Nerada. Literally, the shadows that melt the flesh. Most planets have them, but usually in small clusters. I've never seen an infestation on this scale, or this aggressive."
"What do you mean, most planets? Not Earth?" Donna asked incredulously, but the Doctor replied easily: "Mmm. Earth, and a billion other worlds. Where there's meat, there's Vashta Nerada. You can see them sometimes, if you look. The dust in sunbeams."
Donna stared at him openmouthed before protesting: "If they were on Earth, we'd know."
"Nah." The Doctor scoffed. "Normally they live on road kill. But sometimes people go missing. Not everyone comes back out of the dark." He said darkly and Teresa smacked him, feeling tense enough without his lovely stories.
"Every shadow?" River asked shakily as she pointed her torch down a corridor, and the Doctor corrected: "No. But any shadow."
"So what do we do?" River asked tightly and the Doctor listed: "Daleks, aim for the eyestalk. Sontarans, back of the neck. Vashta Nerada?"
He turned to River and said flatly: "Run. Just run."
"Run?" River repeated incredulously. "Run where?"
The Doctor replied easily as he stood up again: "This is an index point. There must be an exit teleport somewhere."
He and River turned to Lux immediately. The man protested: "Don't look at me, I haven't memorised the schematics."
"Doctor, the little shop." Donna interjected. "They always make you go through the little shop on the way out so they can sell you stuff."
He ran to check it and he said brightly: "You're right. Brilliant! That's why I like the little shop."
He beamed as he ran back to join Teresa and Dave said quickly: "Okay, let's move it."
The Doctor suddenly called sharply: "Actually, Proper Dave?"
The man stopped, and the Doctor said slowly: "Could you stay where you are for a moment?"
"Why?" Dave asked confused, and the Doctor walked up to him slowly as he said softly: "I'm sorry. I am so, so sorry. But you've got two shadows."
Everyone slowly looked down, including Dave, to see the second shadow at a right angle to the original one.
The Doctor explained quietly: "It's how they hunt. They latch on to a food source and keep it fresh."
"What do I do?" Dave asked in a shaking voice, and the Doctor told him seriously: "You stay absolutely still, like there's a wasp in the room. Like there's a million wasps."
"We're not leaving you, Dave." River said firmly.
The Doctor agreed: "Course we're not leaving him."
He then turned back to the man and asked: "Where's your helmet? Don't point, just tell me." He added quickly and Dave answered in a trembling voice: "On the floor, by my bag."
Anita moved to get it and the Doctor warned sharply: "Don't cross his shadow."
Anita moved carefully to fetch the helmet, and handed it to the Doctor who took it just as carefully, murmuring: "Thanks. Now, the rest of you," he ordered as he placed the helmet on Dave, "helmets back on and sealed up. We'll need everything we've got."
"But, Doctor," Donna protested as the archaeologists moved, "we haven't got any helmets."
He agreed easily: "Yeah, but we're safe anyway."
Donna stared at him as she demanded: "How are we safe?"
"We're not." He said tightly. "That was a clever lie to shut you up. Professor," he called to River loudly, "anything I can do with the suit?"
Donna looked royally ticked, but Teresa took Donna's hand carefully, squeezing it and shaking her head minutely to show her that now wasn't the time. Lux demanded: "What good are the damn suits? Miss Evangelista was wearing her suit. There was nothing left."
River interjected: "We can increase the mesh density. Dial it up four hundred percent. Make it a tougher meal."
"Okay." The Doctor said firmly. He used his sonic on Dave's suit, explaining: "Eight hundred percent. Pass it on."
He held out his sonic to River but she lifted one as she replied: "Gotcha."
"What's that?" The Doctor asked, his jaw slacking and his eyes widening.
River replied as though it was obvious: "It's a screwdriver."
The Doctor was looking borderline horrified as he pointed out: "It's sonic."
"Yeah, I know." River replied as though oblivious to his shock. "Snap." She added before moving to upgrade everyone's suits.
The Doctor watched with narrowed eyes before pocketing his sonic and calling out: "With me. Come on."
He grabbed Teresa's hand, and she grabbed Donna's as they ran for the shop. Donna asked excitedly as she pulled back: "What are we doing? We shopping? Is it a good time to shop?"
Teresa jerked the Doctor back as she stopped for Donna and the Doctor urged: "No talking, just moving. Try it."
He dragged Donna and Teresa to a machine pedestal as he said: "Right, stand there in the middle. It's a teleport. Stand in the middle. Can't send the others, Tardis won't recognise them."
He began to work the controls, sonicing them.
"What are you doing?" Donna demanded, and the Doctor explained: "You two don't have suits. You're not safe."
Donna whipped around to face him as she snarled: "You don't have a suit, so you're in just as much danger as I am and I'm not leaving you, and I doubt Terry will either."
The Doctor said firmly: "Donna, let me explain."
Teresa stepped off as he spoke and it was too late as he pressed the button and only Donna disappeared.
"Terry!" He said angrily, and she pointed out: "I have foreknowledge. Did you really think you could fool me?"
"Doctor!" River called and the Doctor made a frustrated noise in his throat as he grabbed Teresa.
"We'll have words later." He told her sternly before they ran back to the Rotunda, where River had called from.
River saw Teresa and she demanded: "Why are you still here? Doctor, why is she still here, it's not safe!"
"River, not now!" Teresa scolded as the Doctor replied tensely: "You think I don't know that?"
"Doctor, focus, look at Dave." Teresa ordered and he did, looking at the man's shadow and he asked with furrowed brows: "Where did it go?"
"It's just gone." Dave replied as the Doctor examined the man. "I looked round, one shadow, see."
River asked: "Does that mean we can leave? I don't want to hang around here."
Lux argued: "I don't know why we're still here. We can leave him, can't we? I mean, no offence." He added to Dave, and River snapped: "Shut up, Mr. Lux."
The Doctor asked Dave: "Did you feel anything, like an energy transfer? Anything at all?"
Dave replied: "No, no, but look, it's gone."
He turned on the spot to make his pointed and the Doctor said sharply: "Stop there. Stop, stop, stop there. Stop moving. They're never just gone and they never give up."
He quickly bent down and soniced the floor around Dave quickly, muttering: "Well, this one's benign."
"Hey, who turned out the lights?" Dave asked, and Teresa's heart dropped. The Doctor looked up as he replied puzzled: "No one, they're fine."
"No seriously, turn them back on." Dave complained, and River answered puzzled: "They are on."
The Doctor glanced back to see Teresa's white face, confirming his fears as Dave retorted: "I can't see a ruddy thing."
"Dave," the Doctor said seriously as he stood back up, "turn around."
Dave turned around, saying in a scared voice: "What's going on? Why can't I see?" Everyone balked as they saw that his entire visor was completely pitch black. "Is the power gone? Are we safe here?"
"Dave," the Doctor ordered urgently, "I want you stay still. Absolutely still." Dave jerked and the Doctor called in alarm: "Dave?"
Dave continued to jerk and shudder as the Doctor called: "Dave? Dave, can you hear me? Are you all right? Talk to me, Dave."
Dave suddenly stopped moving and he replied suddenly calm: "I'm fine. I'm okay. I'm fine."
Teresa's eyes filled as the Doctor said firmly: "I want you to stay still. Absolutely still."
"Doctor." Teresa whispered and he glanced back but froze as Dave repeated: "I'm fine. I'm okay. I'm fine. I can't. Why can't I? I, I can't. Why can't I? I, I can't. Why can't I? I-"
The Doctor turned to see Dave's com unit light as it began to blink and River realized: "He's gone. He's ghosting."
Lux questioned: "Then why is he still standing?"
Dave suddenly said: "Hey, who turned out the lights? Hey, who turned out the lights?"
The Doctor began to lean in and Teresa twisted her hands nervously while River warned: "Doctor, don't."
He ignored her as he asked: "Dave, can you hear me?"
"Hey, who turned out the lights?" 'Dave' asked before he suddenly grabbed the Doctor's throat and shoved him to his knees.
"Doctor!" Teresa cried, taking a step forward as the skull inside Dave's helmet fell forward onto the visor, making it visible to them. Lux took a step back in horror as Teresa reached for the Doctor and River shouted: "Terry!"
River grabbed the blonde girl, keeping her away as the Doctor struggled against 'Dave' who kept repeating: "Who turned out the lights? Hey, who turned out the lights?"
"Doctor!" Teresa screamed and River called: "Excuse me."
She zapped Dave's suit with her screwdriver, forcing the dead man to let go of the Doctor. The Doctor yelled: "Back from it! Get back. Right back."
He grabbed Teresa, pulling her with him as they all backed away from the Zombie Dave as it lurched towards them, unsteady on its feet.
"Doesn't move very fast, does it?" River commented, and the Doctor muttered: "It's a swarm in a suit. But it's learning."
He was staring at the ground where the Zombie Dave was growing four shadows. He pulled Teresa behind him, keeping her with him tightly.
"What do we do? Where do we go?" Lux cried and River asked: "See that wall behind you?"
The Doctor glanced back and River drew a gun.
"Duck." She told them and they all ducked while the Doctor twisted to avoid the beam.
"Squareness gun!" The Doctor cried appreciatively, and River shouted: "Everybody out. Go, go, go."
The Doctor pushed Teresa ahead as River yelled at the others. "Move it. Move, move. Move it. Move, move."
They were back in the darkened aisle room and River snapped at the Doctor: "You said not every shadow."
"But any shadow." The Doctor countered, and they hesitated not knowing where to go but then Zombie Dave called from right behind: "Hey, who turned out the lights?"
"Run!" River yelled as she grabbed Teresa's hand, almost naturally. The Doctor stared at that before quickly running after the two as River led Teresa down the aisles and away from the Zombie Dave.
They eventually stopped in one of the aisles, all the humans gasping and trying to catch their breath as the Doctor began to quickly sonic the light fittings, hoping to keep them going a little longer and a little brighter.
"Trying to boost the power. Light doesn't stop them, but it slows them down." He muttered, and River asked: "So, what's the plan? Do we have a plan?"
She held up her sonic, trying to help, and the Doctor glanced at it while Teresa gasped out: "Since when does he have a plan?"
"Good point." River conceded.
The Doctor ignored the jibe as he murmured, almost accused: "Your screwdriver," he flinched as the light on the fitting brightened, "looks exactly like mine."
"Yeah. You gave it to me." River replied.
"I don't give my screwdriver to anyone." The Doctor corrected darkly, and River retorted: "I'm not anyone."
His eyes narrowed and he demanded: "Who are you?"
"What's the plan?" River asked, ignoring his question.
The Doctor opened his mouth again, when Teresa nudged him. He glanced at her, and she shook her head, so he let the topic go for now as he replied tightly: "I teleported Donna back to the Tardis."
Teresa's shoulders slumped, but neither noticed yet as the Doctor said urgently: "If we don't get back there in under five hours, emergency program one will activate."
River nodded: "Take her home, yeah."
The Doctor frowned as he checked his sonic while River called to the rest of the group: "We need to get a shift on."
"She's not there." The Doctor realized. River turned to him in surprise, and the Doctor said in horror: "I should have received a signal. The console signals me if there's a teleport breach."
River suggested tightly: "Well, maybe the coordinates have slipped. The equipment here's ancient."
The Doctor glanced at Teresa, and she saw. She slowly shook her head and his jaw set. He turned to a nearby Node and called: "Donna Noble. There's a Donna Noble somewhere in this library. Do you have the software to locate her position?"
It turned its head to reveal Donna's face as it said: "Donna Noble has left the library. Donna Noble has been saved."
"Donna." The Doctor whispered in horror, and the Node repeated: "Donna Noble has left the library. Donna Noble has been saved."
River asked in shock: "How can it be Donna? How's that possible?"
The Node continued to repeat as the Doctor touched the face, whispering: "Donna."
Teresa walked over and took his hand. He glanced at her with wide, anguished eyes and she told him gently: "Doctor, I promise you. We will save Donna and bring her back safe."
It was as subtle a reminder she could give him about her tip, as well as her promise. He didn't seem to pick up on the hint as he stared at her pensively, his horror warring with the absolute trust he placed in her and the knowledge that she never made empty promises.
"Hey, who turned out the lights?"
They turned sharply as River called: "Terry! Doctor!"
"Hey, who turned out the lights?" They saw Dave appear around the corner and the Doctor launched into a run, pulling Teresa with him as the others ran past as well, River bringing up the rear.
But they all skid to a halt as the path before them was cast into shadows, the lights going out and they found themselves trapped as Zombie Dace approached from behind, calling: "Hey, who turned out the lights?"
"Doctor, what do we do?" River demanded as she gripped Teresa, holding the blonde girl behind her protectively. The Doctor looked about wildly, searching for an escape as Zombie Dave came steadily closer.