Amy and Raj learn of a scientific experiment designed to see if it can make two people fall in love in the matter of hours. After the gang discusses the viability of the experiment's premise, Sheldon and Penny decide they will test it out to see if it can make them fall in love with each other. The nature of the experiment is to answer truthfully a series of questions followed by staring into each other's eyes without speaking for four minutes. Is there any chance that Sheldon and Penny will fall in love with each other, or at least get to know intimate details about the other that they didn't already know? With Sheldon and Penny occupied with the experiment, Leonard and Amy decide to tag along on Raj and Emily's date, the four who decide to go to an escape room: interactive theater where the participants have to figure out puzzles to escape. This particular room is filled with zombies. Meanwhile, Howard and Bernadette have just arrived at Los Angeles Airport having just returned from Howard's mother's funeral. However, they are missing one important item that was supposed to return to California with them.