Grace had a nightmare about what her life would be like 15 years down the road if she still lived with Will. In Grace's future, her son was rebellious, Karen was married to Rosario, Jack was married to Kevin Bacon and she was miserable with Will.
Leo surprised Grace at the apartment. He had returned from Rome to try and get Grace back. He had no idea that she was carrying his child. He wanted to marry Grace and raise the child together
Two years later, Will and Vince moved in together and adopted a son, Ben. Ever since Grace got back together with Leo, Will had made it a point to never talk to her, again. Vince tried to convince Will to make the first move and call Grace. Meanwhile, Leo wanted Grace to make the first call.
Karen and Jack schemed to get Will and Grace together. The plan worked when both of them rushed to the hospital thinking there was an emergency. Will and Grace realized Jack and Karen's scheme, but agreed to talk over cake in the cafeteria. Meanwhile, Karen and Jack were celebrating their victory of bringing together Will and Grace.

Karen was in a celebratory mood because of her hefty divorce settlement from Stan. When the restaurant bill arrived, her credit card was rejected. Karen found out that all of Stan's money was borrowed and her settlement money was useless. Karen was broke.
After Will and Grace had a wonderful reunion dinner with Jack and Karen at his apartment, he wanted to see more of Grace. They tried to correlate their schedules, but Will's top priority was Vince and his baby, Ben, while Grace's top priority was Leo and her baby, Lyla. They figured fate would bring them together, again.
Karen's nemesis, Beverly Leslie, offered Jack all of his money to be his boyfriend. With Karen broke, Jack needed another source of income, so he started to date Beverly. Now, Karen wanted Jack to take care of her, the way she'd taken care of him. Later, Beverly died in a freak accident and Jack became the sole heir to his fortune. He agreed to help Karen out.
Many years later, Will and Grace were right. fate would bring them together! Their two kids, Lyla and Ben, lived across the hall from each other in the same dorm at college. While Will and Grace were each helping Ben and Lyla move, they ran into each other. They played catch-up in the college cafeteria, over cake.
Jack and Karen grew old together and they each took turns taking care of Rosario. They discussed how their relationship had outlived any marriages or boyfriends they'd ever had. They ended their night with a song, Nat King Cole's UnforgettableLyla and Ben were getting married and Will and Grace couldn't have been happier. They celebrated with Jack and Karen at one of their favorite bars. Will delivered a speech about the importance of friendship and being there for one another.