Mike Bartlett’s curious blank-verse drama Charles III became an international hit. His new effort examines the cut-throat world of dark-web espionage. An American traitor named Andrew (Edward Snowden presumably) is hiding out in a Moscow hotel. Enter a flirty, giggling Irishwoman played by Caoilfhionn Dunne, who claims to be British and who teases Andrew over his betrayal of his homeland’s secrets.