Major turning points?

The major turning point comes when Mrs. Marwood hears Mrs. Fainall talking. During their discussion, they reveal Mirabell's plans, and the fact he's had an affair with Mrs. Fainall. Unfortunately for mrs. Fainall, Mrs. Marwood also hears a number of insults directed toward herself, causing her to pass on all of the information she gathered to Mr. Fainall. From this point foward, Fainall is in charge of the action.