Doctor Who episode 012 - The Edge of Destruction

Something has caused the TARDIS console to explode in mid-flight, plunging the ship into darkness and rendering the crew unconscious. As they slowly recover, they find themselves suffering from loss of memory and odd headaches. The TARDIS behaves oddly, as the doors open and close of their own accord. Has the ship been possessed in some way, or is something more dangerous happening to the time travelers?