The high point of "Single Spies," a pair of plays by Alan Bennett receiving an American premiere at the Rhino, is a chance meeting, in A Question of Attribution, between Sir Anthony Blunt and the queen of England. Blunt is an exposed Soviet agent working (by royal dispensation) as Queen Elizabeth's art curator, with an illustrious independent career as an art historian. He's played terrifically here by John Fisher as a swish and snobbish English mandarin, with an accent worthy of the queen's service and a habit of wielding his spectacles in one hand to make a point. Libby O'Donnell plays the queen in a crass, flat, shopkeeper's-daughter mode -- not at all regal, but very funny. Their little chat on the topic of forgeries and fakes turns neatly into a veiled warning about treachery, much to Blunt's surprise. "Be careful of how you go up the ladder, Sir Anthony," says the queen on her way out, referring to a stepladder he's positioned in front of a dodgy Titian. "One could have a nasty fall." In real life, when Thatcher came to power and ended Blunt's in-house immunity, in 1979, he did suffer a nasty fall; but for 30 years he'd lived far above the level of his former comrade, Guy Burgess, whose defection to Moscow he'd arranged in 1951. Burgess is the subject of Bennett's other play in this pairing, An Englishman Abroad, and we see him going to seed in a Moscow apartment. Both plays suffer from too much talk, too much explanation, and too much arch acting -- there's an almost sarcastic devotion to Englishness here -- but as a study of witch hunts and official hypocrisy in Cold War England, Bennett's writing holds up wittily well.