Leonard has come home a few days early, surprising Penny. The one person who isn't surprised is Sheldon, as Leonard hasn't told him and doesn't want him to know so that he and Penny can have a few days alone together. However, when Sheldon sees what he considers unusual activity in Penny's apartment, he thinks that Penny is having an affair. Meanwhile, Howard has been putting on a few pounds of late, and is being really cranky about it. Bernadette, the scientist, figures out why. There is nothing they can do about Howard's problem in the short term, and will have to endure a couple of weeks of bloating and moodiness. Howard, however, gets some unexpected support with what he considers his primary problem.