'The Devil's Chord' on 'Doctor Who': Your questions answered

Doctor Who is back with a new Doctor (Ncuti Gatwa), a new companion in Ruby Sunday (Millie Gibson), and a whole new season of time-travel adventures, courtesy of returning showrunner Russell T Davies. With scads of past seasons of lore to pull from, Season 14 started off strong with "Space Babies" and "The Devil's Chord," a double-header that took audiences to a far-flung future and a mop-topped past. Lucky for us Whovians, both episodes are rich with Easter eggs.

The first Easter egg in "The Devil's Chord" is the tritone itself...