This series, already so impressive, this season has quantum leapt over itself, becoming a TV series that pulls you in, holds you tight, and never lets go. Two weeks ago, it was David’s descent into a surrealistic rabbit hole. Last week, it was a mesmerizing trip through, and through and through again, the maze that is Syd’s mind. And tonight, most of the hour is devoted to Aubrey Plaza as Lenny, who has identity problems and psychedelic visions of her own, as she seems to return from her psychic prison. But has she returned? And is she… she? A couple of classic and very appropriate rock tunes are included in tonight’s installment, but they could have found room for at least one more: The Who’s “Behind Blue Eyes.” I’m just saying…