Elizabeth had a secret lover? That was a situation I didn't see coming, especially with an asset. I would have guessed that she was too uptight to do something like that. Even more shocking is that Philip had no clue about his wife's escapades with "Gregory."
The introduction of Gregory added to the complexity of the Soviet spy network operating in the United States. He's not only an American working for the KGB; he's in love with Elizabeth. He had his own crew to help with assignments, but unless I heard it wrong they don't realize he's a Soviet asset.