What quest does George Wilson go on in Chapter 8?

George Wilson goes on a quest to kill the man he believes responsible for Myrtle's death. When the quest is over, he takes his own life as well.

The police, on the strength of what he said to Michaelis, that he ‘had a way of finding out,’ supposed that he spent that time going from garage to garage thereabouts inquiring for a yellow car. On the other hand no garage man who had seen him ever came forward—and perhaps he had an easier, surer way of finding out what he wanted to know. By half past two he was in West Egg where he asked someone the way to Gatsby’s house.

The chauffeur—he was one of Wolfshiem’s protégés— heard the shots—afterward he could only say that he hadn’t thought anything much about them.