TheDoctorfacestheendofhislifeastheMaster'splanshurtleoutofcontrol.Withthesoundofdrumsgrowinglouder,andanancienttrapclosingaroundtheEarth,theDoctorandWilfmustfightalone.Butsacrificesmustbemade,andthedeadlyprophecywarns:"Hewillknockfourtimes."eee