The first episode of the return of “Killing Eve” was, I felt, flat (see my review). And the second episode simmers for a while, and then … (at last!) Eve’s got another assassin to pursue, injured Villanelle finds sanctuary with a man whose fate we dread, and the lurid express accelerates and, over the first half of the season, never looks back. Sandra Oh is magnificent as combusting Eve and Jodie Comer out-Villanelles her earlier performances, magnetic as petulant, psychotic, and unpredictable as we want her to be. Dread and delight mix as we plunge onwards.