Err...
The Doctor screamed and clutched at the headpiece.
Martha watched and shouted, clutching at the bars that separated them.
The Doctor was changing, he became someone else, and again and again.
And all the time, he was laughing at them.

"Doctor!" Martha broke down the door, and ripped the headpiece off his head. She looked down at the frail white-haired man the machinery had created with the Doctor's body. He looked up at her through aged eyes.
"Doctor, what has he done to you?" Martha whispered, brushing the white hairs out of his eyes. His mouth parted, and he spoke.
"Is that you Susan, hm?"

Oooooooo!

Oh, and Russel T Davies is incompetent.