Sherlock Season 4 Finale: 13 Dumbest Moments From 'The Final Problem'
4. Watson Is Chained Up... Until He Isn't
Moving the action to the old Holmes home (which is maybe where Eurus was based all along, unless she really did orchestrate them all being transported there), and in what we learn is a mirroring of what Eurus did to Redbeard, poor old John Watson is stuck down a well.
The water is rising, there are bones on the floor, and he's chained up. This would make any potential escape or rescue seemingly problematic. But not for Watson, apparently. When Sherlock has found Eurus and talked her round, a rope is thrown down the well, and Watson climbs out no problem - with no reference to the chains he was previously bound by. Good trick, that.