Doctor Who: Every Series Plot Thread Ranked Worst To Best
3. He Will Knock Four Times
This small riddle only ran for a handful of specials, but it packed one hell of a punch. You can't help but love Russel T Davis' writing.
Four knocks... Well, that sounds awfully like The Master's drumbeat. Case solved, huh? Nope. Not by a long shot, Davis was about to say goodbye to the show, but not before pulling one final rouse. Take the godly spectacle of Doctor versus Master versus Time Lords, shove all that to one side, and make David Tennant's own parting of the ways about nothing more than one old man trapped inside a radioactive box. It's not that The Doctor wants to give up his life, it's that he has to.
Leading to a regeneration in the most emotional way imaginable, this entire thread was genius from start to finish. The misdirections were clever and the premise was really based on nothing other than pure humanity, something Russel excelled in. It was a small clue which led to a big event, and final episodes don't get much bigger than this one.
Plot threading of the highest order... Okay, third highest.