Season 3

Raj comes to the table with the others in the cafeteria and has to sneeze. Immediately, Sheldon expels him from the table. The others consider him to be too strict, although when Raj sneezes again, they want him to sit somewhere else as well. Sheldon informs Leonard that he is having a female guest for a couple of days. She is Dr. Elisabeth Plimpton. She is a cosmological physicist in Princeton and is being considered for a position at the University. Leonard is enthusiastic because he is a big fan. She is going live in Sheldon's room, while Sheldon will use the sofa. Leonard asks why she does not sleep in a hotel, but Dr. Plimpton seems to have the same aversion to strange beds as Sheldon.

When Sheldon leaves, Raj is allowed to sit at the table again.

Sheldon comes into the staircase and meets Penny there. He has bought a lot of women's articles and is not sure whether he has bought the right things. He asks her for some advice. Penny is astonished when she learns about Sheldon's visitor and Sheldon tells her about Dr. Plimpton. He asks her not to bother her with women talk.

When Dr. Plimpton knocks on the apartment's door, Leonard and Sheldon are very excited. However, Elisabeth is relaxed and nice and Leonard seems very embarrassed. He is courteous and flattering, while Sheldon repeatedly reprimands him. When Sheldon brings his guest to his room, he explains his inventory and the emergency supplies in the closet to her. However, Elisabeth is more interested in Leonard.

Elisabeth knocks later at Leonard's, who is lying in bed reading her book. Elisabeth makes unmistakable innuendoes and removes her clothes while quoting a chapter.

The next morning, Leonard and Elisabeth come into the kitchen together. Sheldon asks her about her sleep and does not understand why both laugh. Then Penny knocks. She has a problem with her car and needs a driver. Leonard agrees and Sheldon introduces her to Elisabeth. Penny understands the situation quickly and encourages Leonard, telling him that it is ok to sleep with Elisabeth. Sheldon is shocked, because he did not count on anything like that. Penny prefers to take the bus and goes.

Raj, Howard and Leonard are eating in the cafeteria. Leonard wants to tell the other two about his adventure and tries to bring it up by hinting. However, neither Howard nor Raj get the truth. Then, Sheldon and Elisabeth come and he introduces her to everyone. They sit there and when Leonard wants to take coffee for Elisabeth, she makes insinuations about Raj.

Howard knocks at Raj's, but he won't let him in. Then Elisabeth calls the flat saying Howard should come in. Howard is astonished when she invites him to take part in a role playing game. Raj and Howard are beside themselves and Elisabeth changes her clothes. Leonard shows up. They had planned a Halo evening. Elisabeth sticks her head out of the door and suggests a new role playing game for four. Raj sends Howard and Leonard to the corridor with an excuse and quickly closes the door behind them. Then he turns to Elisabeth.

Penny and Leonard find each other at the corridor and Leonard wants to talk to Penny about his affair. He wants to justify himself, but Penny pacifies him.