The gang decides to have a re-wedding for Leonard and Penny at the Wolowitz House since their first one was a bit of a mess. Stuart and Alex begin a relationship after meeting and talking.
Howard and Bernadette admit to Penny that they knew all along about Leonard's accidental indiscretion with Mandy Chao on the North Sea and they also reveal to her and Leonard that Sheldon ruined their ceremony through the TV and what he did. Penny gets upset with Howardette and Leonard and Penny get so angry at Sheldon that they call his mother to tell her. Later in Apartment 4A, Leonard, Sheldon, Howard, Raj, Penny, Bernadette, Amy, Stuart, Emily and Alex who has joined the group and who after meeting Stuart and talking with him, began dating him after finding out they have some things in common. Everyone suddenly starts arguing about the messed-up wedding and secret-keeping until suddenly Sheldon's mother, Mary Cooper walks in, sees the friends fighting and shouts "Quiet!", startling all 10 friends.
Everyone but Leonard and Penny is surprised to see Sheldon's mother. She introduces herself to Bernadette, Stuart, Emily and Alex and first reprimands Sheldon for what he did and he is not at all happy that Leonard and Penny told her what he did during the Lenny wedding ceremony through through TV and that he insulted Amy near the end which caused everyone, but Howard and Stuart, to miss the final moments. She takes them all to sit down and they all decide to try and resolve everything. After a little discussion, everyone forgives each other, they all become friends again, including Penny with Howard and Bernadette and Leonard and Penny with Sheldon and Lenny apologizes that they eloped. Mary proposes a re-wedding and everyone thinks it's a great idea and so they all begin planning.
After one week of planning, the re-wedding takes place at Howard and Bernadette's house in the garden on a beautiful sunny day with the guests being Mary, Dave Gibbs, Claire, Penny's parents, brother, sister, brother-in-law and nephew (all who flew in to Pasadena from Nebraska), Mandy Chao, Leonard's father (who flew in from New Jersey), Leslie Winkle and Wil Wheaton.
At the end, everyone is seen at the reception and having a fun time dancing, talking, eating and drinking and a photographer taking photographs of Leonard and Penny, the rest of the gang and the guests, together and separately.