"I can't believe you got us locked up again," Donna said, peering through the bars of their cell.

"Me? It was you this time!" The Doctor didn't look up from where he was working on the bars with the sonic screwdriver. "You just had to say it was a bit chilly! I gave you my coat."

"Well, it was chilly! And how was I supposed to know it was an insult? Honestly, you could give me a clue about these things."

"Well..."

"Admit it - you didn't know either! That great big Timelord brain of yours, and you didn't know that."

"Well, I can't know every custom of every world, can I? What would be the fun of traveling to see them if I already knew everything?"

"Should be a guidebook or something," Donna muttered. "Or a frequent-prisoner club."

He looked up at her. "You are keeping watch, aren't you?"

"Yes, I am. Hurry up and get us out of here!"

"I'm working on it. Just keep an eye out."

"Do you think they'll feed us anything? I'm starved. Someone burned my toast this morning with the upgraded toaster." She looked pointedly at him, but he studiously avoided her eyes.

"Check my coat pockets - I think there's a packet of biscuits in there." He gestured to his coat draped over the chair. He turned back to the bars, muttering, "Must get that temperature control fixed."

Donna rummaged through the pockets. "How do you keep so much stuff in these? Aha, biscuits!"

"Timelord technology. They're bigger on the inside." He shrugged.

"Dead useful." Donna ripped open the packet, and munched on a biscuit. She took another out of the packet and dangled it in front of his face. "You should eat something, too."

He took it from her, stowing the sonic screwdriver in the pocket of his suit. "Thanks." He sat back on the concrete floor.

Donna sat down opposite him. "So, you're an alien."

The Doctor raised his eyebrows at her. "Haven't we been over this? Besides, from where I sit, you're the alien."

"Right, right." Donna waved her hand dismissively. "I'm curious, though. I know you've got that big brain, holding all of time and space and all that, but physically you look human. So, is there anything, well, alien about you I should know about. In case you end up in the hospital or something, you know."

He brushed crumbs from his shirt, thinking. "Well, you should probably know I have two hearts. That might be important."

"Two hearts?" Proof that he was from another world. After all she had already experienced with him, this somehow seemed the least unusual.

"Yes, two hearts." He smiled, and reached out to take her hand, pulling it to him to rest first on one side of his chest, then the other. Donna could feel two distinct heartbeats. She looked up to meet his eyes, hand still on his chest. "Why, that's incredible!"

"Perfectly normal for me," he said, his hand still covering hers, holding her gaze. "And I have a respiratory bypass system, that often comes in handy."

Donna nodded, then realized her hand was still on his chest. She pulled it away quickly.

"Are you alright?" he asked.

"I'm fine." Two hearts. "So, have you got two of anything else I should know about?"

He grinned. "No."

Donna felt herself blush, but grinned back. "Well, then, I suppose we'd better get back to our escape plan, hm?" She stood and resumed her post as lookout, and he pulled out the sonic screwdriver again. Soon enough they were free, off and running into the unknown. The toaster still burned the toast most of the time, but Donna soon had a new coat with pockets that were bigger on the inside.