After one insensitive and self-serving move too many by Sheldon, Leonard has had it with him and decides to move out, even throwing the roommate agreement into the garbage. While Sheldon doesn't understand or want Leonard to move out, Sheldon will not apologize for what he sees as no wrongdoing on his part nor will he beg Leonard to stay. Unilaterally, Leonard decides to move in with Penny, who doesn't have the confidence to tell him that she doesn't want him to move in since she doesn't believe their relationship is yet at that stage. With an extra bedroom now in Sheldon's apartment, Amy sees it as her opportunity to get closer to Sheldon by becoming his new roommate. Sheldon, in turn, doesn't want Amy as a roommate, although he can't tell her not to move in since all her arguments are logical, and thus ones he can't refute. Will Penny and/or Sheldon eventually accept their new roommates, or will this new set-up cause problems to make Leonard and/or Amy reconsider? Meanwhile, Howard convinces a reluctant Raj to look after his mother while he and Bernadette are out of town. Raj ends up feeling like a second Howard, who can't physically leave Mrs. Wolowitz's house.