Tom Wilson became aware that Myrtle is having an affair, or at least was involved in something of which he did not approve and was taking steps to bring to an end.
My wife and I want to go West....She's been talking about it for ten years...And now she's going whether she wants to or not.I'm going to get her away....I just got wised up to something funny the last two day," remarked Wilson. "That's why I want to get away.
In the aftermath of the arguments that took place between George and Myrtle as he has been confronting her with his suspicions, George locked Myrtle in the office over Wilson's garage. Nick observed her looking down through the window and saw Tom talking with George, while Jordan Baker sat in the passenger's seat beside Tom.
When Michaelis stopped by the garage around five in the evening, he found Wilson, looking pale and "shaking all over" in his downstairs office while
a violent racket broke out overhead. "I've got my wife locked in up there," explained Wilson calmly. "She's going to stay there till the day after tomorrow, and then we're going to move away."
However, Myrtle did get downstairs - Michaelis heard her shouting shortly after seven. "Beat me!" he heard her cry. "throw me down and beat me, you dirty little coward!" Fleeing from George after this taunt, she ran out of the garage and into the road - and the path of the oncoming car.