Plot

As part of a well-deserved holiday, the Doctor takes a tour on a planet called Midnight. Little does he know that something is knocking on the walls, although the planet shouldn't be inhabited. Soon the passengers begin to panic when one of them is possessed.

The Doctor and Donna are taking a bit of a break from their adventures and spending a bit of time on the planet Midnight. While Donna opts to spend a bit of time in the spa, the Doctor goes off on an all-day bus tour to the Sapphire Waterfall. Part way through the four hour journey to get there, the vehicle stops for no apparent reason. When they hear noise coming from outside the vehicle, panic begins to set in. When one of the passengers is taken over by the being, the passengers paranoia and fear know no bounds and the focus of their solution is to eliminate the Doctor.—garykmcd

While Donna stays getting pampered, the Doctor goes onto a plane/spaceship without her. Everything is fine until the knocking on the wall begins. With a woman on the ship who has the ability to turn all his powers against him, passengers who are willing to throw him out of the ship and a unknown alien possesing everyone, will the Doctor and passengers ever get out alive?