Returning from a dinner with the rest of the guys, Leonard and Sheldon are shocked to get back to a robbed apartment. Fearing the criminals will return, Sheldon becomes paranoid and locks himself in his room during the night. Realizing something has to be done, they get help from Howard and Rajesh in order to create a state-of-the-art security system that will attack any criminals that try to enter their apartment in the future. However, the security system can't help Sheldon's paranoid reaction to the breaking-and-entering, causing him to move to Bozeman, Montana, but will he return?