Nobody pulls the reins in on Diane. Her ex-husband Ken learned that lesson in Things Change 3. Now it's her lesbian lover Mike who learns a lesson or two. While Mike is having jealous delusions of Diane and Pete, Diane is really breaking free with Bille, Mike's ex-lover. Confused? Imagine how Ken feels when Diane comes crawling back to him, with Billie in tow for a three-way marriage!