The last time that had happened - some twenty-four subjective hours ago - the Master was forcing a landing, searching for a body. Somehow he'd survived cremation by the Daleks, pulling his plasma form from his own ashes, and now had needed a body to possess. He had taken a human's, temporarily; requiring something sturdier, he'd then plotted to take the Doctor's.
And the whole adventure had ended with the Master being sucked into the workings of the TARDIS.
"Oops," said the Doctor.
The TARDIS chuckled evilly.
THE END