Leonard angers the University and the Physics Community when he gives an embarrassing radio interview. Bernadette and Amy talk about their success. After the embarrassing radio interview Penny comforts her husband.
Leonard is devastated by the new friendly relation developing between his mother and Penny. Meanwhile Sheldon takes a detour with Raj and Howard to explore the old belongings of Howard's Science Models.
Howard and Leonard become upset after they discover that Sheldon has been working with the military without telling them; Bernadette asks Raj to investigate her suspicions that Ruchi is attempting to take her job away from her.
Sheldon and Amy try to eliminate stress from wedding planning by applying math to the process ending up at city hall. Also, Raj "breaks up" with Howard after realizing his best friend is actually hurting his confidence.
Sheldon and Wolowitz plan birthday celebrations for Amy and Halley, respectively. But later things go wrong. Amy and Sheldon get sick during the party and Raj help Wolowitz plan for the but later on things went wrong when they quarrel which put their friendship in jeopardy but later they find ways to get along.
Sheldon and Amy pick their best-man and maid of honor, by doing tricky experiments on their friends. This causes uproar in the group. Meanwhile, Leonard's self-confidence is still badly damaged after reading his brother's Christmas letter.
Sheldon kicks Amy out to work solo, so she and Leonard bond during a series of science experiments; Howard is replaced by Bert in Footprints on the Moon; Penny proves to be a surprising source of scientific inspiration for Sheldon. Howard and Raj start a band.