He flung open the grating under the console and started madly pulling pieces of equipment out, muttering to himself. Donna watched him, in the blue suit, no tie, and wondered if his single heart was pounding as hard as hers was. "Doctor?" she said, unsure if he would answer to that name, now that he was half human. Partly her. Did that make him her son?

He looked up at her with a grin, waving a large, unidentifiable piece of equipment triumphantly. "Aha!"

"What are you doing?"

"Making a weapon, of course," he said, distractedly.

"A weapon?" Not the Doctor, then. Different. Her Doctor would never build a gun, and that was exactly what he was building. Not that she could see an alternative at the moment. She thought of the others, wondering if the Doctor thought she was dead. She felt sick at the thought.

He looked up at her, and he seemed suddenly young, a little unsure, and she stepped quickly to him, placed her hand on his arm. She could feel him, warm, under the fabric. "What's the plan?"

"No idea," he said solemnly. He put the tools down, pressed his hand to his chest. "One heart, beating so fast." His voice was soft, wondering.

She put her hand over his, squeezing reassuringly. "You'll get used to it." She hoped she was right.