The Doctor had no idea how long he'd been trapped under the ground. It had likely been weeks, and as every minute passed he was becoming more and more convinced that Valek was just waiting for him to welcome the change that was inevitably going to happen. Valek wasn't going to let him die; he was going to make him wait, and wait... but the Doctor's mind was stronger than those of the humans the great vampire usually targeted, and he wasn't going to give in so easily.
He shifted slightly as he heard the entrance bang open, assuming it was Valek returning to taunt him or something similar. It was only when he heard the familiar voice that the Doctor bothered to make any sort of effort. He groaned against the cloth that was placed in his mouth now that the silence had apparently come to an end. Valek wasn't stupid enough to leave him with the ability to scream and shout. All he could do was make vague sounds of distress to attract the Master's attention.