Last week’s Season 5 premiere of Luther, in which Idris Elba returned as volatile police investigator John Luther, took the entire hour to bring him face to face with his former nemesis and object of fascination, Ruth Wilson’s Alice Morgan. But when the door was opened just before the credits rolled, and Alice was on the other side – very much alive, much to Luther’s surprise – it set things up for a juicy episode that should pick up in high gear from the very first frame.