On the season finale of The Big Bang Theory , “The Status Quo Combustion,”
Penny and Leonard announce to the group that they are engaged and Raj also shares his news that he had sex with Emily. The group seems more excited for Raj, since as Bernadette says, Leonard and Penny propose to each other all the time.
Sheldon tells the group that the college won’t let him change his field of study from string theory since that is what he was hired to do and what his grant is for. This leads him to consider leaving the university.
Bernadette and Howard come to the conclusion that they may have to live with Mrs. Wolowitz since the nurses keep quitting.
Leonard video chats with his mom to tell her that he is engaged. She already knows because Sheldon had told her. She says she approves because Sheldon approves. This upsets Leonard because Sheldon’s opinion matters more than his.
Penny calls her mom to tell her about the engagement. She has to remind her of who Leonard is. Amy asks Penny what the living arrangements would be. Penny is unsure since her and Leonard didn’t speak about it yet.
Bernadette realizes Penny doesn’t have a job, so she offers to pay her anything to take care of Howard’s mom. Penny agrees, but quits after taking care of her for a very short period of time.
Leonard brings up future living arrangements with Sheldon. Sheldon assumes that Penny would live with them and he is willing to allow her to stay there one day a week on a trial basis. Leonard explains that he would want to live with Penny without him. He suggests that he would either move in with Penny, or Penny can move into their apartment with Sheldon moving across the hall. This enrages Sheldon.
Sheldon complains to Amy about the university and Leonard. Amy tries to convince him that living alone may be good since Leonard annoys him. Amy also suggests that she can live with Sheldon if he doesn’t like living alone. Sheldon scoffs at this idea.
Leonard cooks for Penny and they talk about a wedding date. Amy comes in looking for Sheldon. Leonard tells her he probably just needs some alone time. Amy agrees and then barges in on their dinner. Leonard tries to drop hints for her to leave, but she isn’t getting it. That is, until Penny tells her to get out.
Sheldon shows up at the comic book store and sees that everything was burned from a fire that started when Stuart was cooking in the back and temporarily left. Sheldon hates that everything is starting to change.
Leonard finds out that Sheldon is at the train station alone, so he and Penny go to find him meanwhile, Howard and Raj show up and see the comic book store burned. Howard asks if he did this for the insurance money. Stuart says he is tired of being asked that. Stuart asks if he can stay with Raj, but Howard gives him an offer to stay with him to take care of his mom.
Penny and Leonard find Sheldon getting ready to “get on a train and leave forever.” Leonard tries to make him feel better, but nothing seems to work. Sheldon tells Leonard that everything is changing and he needs to get away and think. Penny takes Leonard aside and tells him maybe they should let him go, that it might be good for him. Leonard is reluctant, thinking Sheldon won't be okay on his own, but he eventually agrees. They say their goodbyes and leave Sheldon at the train station.
Stuart walks in the see Howard and Bernadette sitting on the couch. He asks them what they are still doing there, they should go home and not worry. They are shocked that Stuart is doing so well. He says he loves taking care of Mrs. Wolowitz, who he calls by her first name, Debbie, and that the job is a dream come true.
Sheldon checks in with Amy while she is with Penny and Leonard. After getting off the phone, Amy beats Leonard with a pillow, yelling at him for letting Sheldon go.