Season synopsis
Contains spoilers for this season and earlier seasons.
After Leonard and Penny repeat their Las Vegas vows for family and friends, the season settles into the awkward logistics of married life. When Amy's apartment floods, Sheldon agrees to test living with her in Penny's apartment, treating daily routines as an experiment. Living together brings arguments over sleep, schedules and Sheldon's need to control their surroundings, but they adjust and continue sharing the flat after Amy's repairs are finished. Sheldon and Amy's move gives Leonard and Penny a home of their own, though they still have to negotiate what to change and how to make time for each other.
Howard and Bernadette prepare for parenthood while balancing work and doubts about whether they are ready. Their daughter Halley is born during the season; Bernadette struggles with sleep and the prospect of returning to her demanding job, while both parents worry about leaving the baby in daycare. Raj, meanwhile, finds himself single again and convenes several former girlfriends to ask why his relationships fail. His father points out how much of Raj's expensive lifestyle he funds, so Raj gives up his apartment, moves in with Leonard and Penny, then rents a room from geologist Bert. The guys also work together on a guidance system for the Air Force.
Amy leaves Pasadena for a summer research fellowship at Princeton, and Sheldon tries to support her while they manage the distance. With Amy away, Ramona Nowitzki returns to Caltech and grows close to Sheldon; Penny and Bernadette recognize her interest before Sheldon does. When Ramona finally kisses him, Sheldon leaves immediately, flies to New Jersey and appears at Amy's door with the ring he has kept for years. He proposes, ending the season on Amy's unanswered reaction rather than on a wedding or an acceptance.