In chapter 2 Tom asks Nick to take a ride with him into the city. On their way through, they stop at George's garage where Tom and George discuss a car that George could really use. When George leaves the room for a brief moment to get a chair for them to sit on, Tom makes arrangements for Myrtle to sneak off to New York on the next train. He does this right in front of Nick. So Nick is introduced right away to the fact that they are having an affair. Earlier it was one thing to know that he was taking phone calls at his own home from "another woman," but this was definitely a very blatant move that helps create the true character of Tom according to the way Nick sees him.
Nick meets Tom's mistress, Myrtle when they go into the city for lunch. They get off the train early and go to the gas station where her husband Mr. Wilson works. They meet and introduce themselves and then go to their apartment in the city. They have a party at the apartment and get a dog
in the city