Not only is Charlie having a great time with his mother at the event, he's being exposed to a lot of wealthy hot woman.
Alan gets wind of all the fun they've been having together and grows increasingly jealous.
At the event Evelyn introduces Charlie to a charming woman with whom he hits it off. However, Charlie feels as if he must choose between spending time with Evelyn or this new lady.
Of course, Charlie picks the woman over his mother, only to have the audience discover that Evelyn orchestrated the whole thing in order to have the husband find his cheating wife with Charlie. This would break up the marriage allowing Evelyn to sell their house.
Charlie and Evelyn used each other to get what they wanted, and in this case, Evelyn outplayed him.
Meanwhile, Alan begins dating a "damaged" woman who constantly weeps after sex. After seeing a therapist and getting back on her meds, Alan gives the woman another chance only to be faced with the same results.