Chameleon Circuit

"Doctor?" Amy worried, "Where are we?"  

"Stay RIGHT THERE Amelia," he instructed, "Do NOT leave the TARDIS, do you understand me?"  

"Why not?" she demanded.    

"There are flesh eating creatures in the shadows," the Doctor explained calmly, "They are called the Vashta Nerada. Like... A thousand THOUSAND million pirañas in the air. You are safe as long as you stay in the TARDIS, okay? I parked it right outside where I need to be, so I'll be alright. Please. For once, just stay here."  

"Why?" Rory blinked, "What are you doing?"  

"In my last life," the Doctor explained, "When I first met River, even before you  Amelia, She'd been given my screwdriver... That was last night, at least from her perspective. I'm here to get her back... Along with her friends."  

"We'll stay here," Rory promised, "But if you aren't back in five minutes..."  

"Got it!" the Doctor ran out, before he could finish. Running up to the library controls, he fished out his older sonic screwdriver - from his previous life - and stuck it into the outlet to give it the small boost he needed and flipped a few switches before jumping in the TARDIS and quickly setting the coordinates for the front lobby. Once the door was open, it didn't take very long for the explorers to hop into it, River slamming the door behind her.   

"Hello Sweetie," she smirked at him. He didn't waste a second, holding her so tightly that everyone held their breath, not wanting to risk spoiling the moment.   

"I hate it when you do these silly adventures," he said, at last, pulling away from her and standing at arms length.   

"No you don't," she chuckled.    

"No I don't," he agreed.   

"Now who's this?" the one man, Dave, demanded.   

"This is the Doctor," River explained.   

"I thought that other bloke was the Doctor," the other Dave frowned.   

"Yes," the Doctor turned to the console, starting her up and getting out of there, "That was me, too! Well, younger me, at least!"  

"What happened to the nice lady?" Miss Avengelista tilted her head to one side. River bit her bottom lip, looking between her and the Doctor, hesitantly.   

"Donna," he arched his back, pain filling his words, "Can't travel with me, anymore... It's for her own safety."  

"Why?" Anita questioned.   

"Because!" the Doctor snapped, turning towards them with anger in his eyes, "Otherwise, her mind will explode and she will burn and die!" There was a frightened silence before the Doctor turned back and slumped his shoulders, "I'm sorry... Let's just... Go."