If that sharp note in the Doctor's voice was meant to put the Master in his place, it had quite the opposite effect. He could sense the hurt behind it, and beyond that, the tension. The worry. And it just made him want to push the Doctor further, cement his helplessness in his mind. Break him.

The Master was grinning fiercely, not to mention slightly flushed, by the time he took his finger off the trigger. "Will you look at that," he said, laughing a little and kissing it. "It works!"

And then he graced the Doctor with a cruel, more restrained smile, his childish glee slipping away like another mask. "On that setting, anyhow."

He fiddled with the screwdriver again, before bringing it back up to fire. "Ooh. Let's see what this one does, Doctor!"