In The Great Gatsby, what excuse does Myrtle use to see Tom?

In Chapter 2, when Myrtle agrees to see Tom, Nick asks him if George (Myrtle's husband) ever objects to Myrtle going out. Tom explains that Myrtle tells George she is going to visit her sister in New York. Evidently, this is her excuse each time she goes to be with Tom. Tom arrogantly claims that George has no idea about the affair. "He's so dumb he doesn't know he's alive." 

George will eventually discover that Myrtle has something going on, and perhaps he had suspicions of this early on. He always appears despondent and tired. In Chapter 7, when Daisy, Gatsby, Nick, Tom, and Jordan go into the city, the latter three stop at George's garage. Nick observes and reveals that George has come to this discovery that his wife is perhaps having an affair. George even claims that he will be taking Myrtle out west. He evidently wants to get away from his depressing garage in the Valley of Ashes, and more importantly wants to get Myrtle away from the man she's been seeing. By this point, George still doesn't know who it is. In fact, he will never know that it is Tom. By the end, he concludes that it is someone else.