Stuart asks Leonard for advice after telling him that he is having a second date with Penny. Leonard, however, doesn’t want Stuart to go further with Penny. Stuart manages to get Penny drunk but he discovers that Leonard and Penny might be into something after Penny blurted out Leonard’s name.

Meanwhile, Howard recognized that he made a critical error on the space toilet that he invented, and that it will dispense its waste through the ISS instead of outer space. He asks Raj and Sheldon to help him construct a fix with materials that are readily available on the ISS, and they were able to manage the fix. They eventually do throw together a fix. The episode ends with all of the ISS astronauts asking to go on a spacewalk, presumably because their waste has leaked out of the toilet, causing the inside of the station to stink