S9E20 7 April: The Rodent Infestation. Raj moves in with the Wolowitzes after his apartment's area becomes infested with rats. Stuart, left on the streets due to his apartment being caught in it, finds a lost lottery ticket, the winning one. He uses it to build a better comic book store. Sheldon and Leonard host a video games tournament. Title: Raj's and Stuart's apartments are infested with rats.
S9E21 21 April: The Accidental Hero Manipulation. Stuart ends up creating many jobs with his new comic book store, but Capital Comics owner Jesse tries to make up a story making him responsible. The gang turn Stuart's room into an alternate hangout room. Emily and Raj struggle to maintain their relationship. Title: Stuart accidentally creates many jobs but is manipulated by Jesse.
S9E22 5 May: The Bed-Ridden Astrophysicist Hippocampus Malfunction. After taking her for a walk, Raj loses Cinnamon, causing him to be bed-ridden for days. The gang create a website for beginners to engage in science, but they disagree heavily. At the end, Lucy, Raj's ex-girlfriend, shows up at the old apartment with Cinnamon. Title: Raj loses Cinnamon due to not remembering where he left her pram. Memory involves the hippocampus in the brain.
S9E23 19 May: The Brake Failure Reaction: Leonard hears his brother Michael is caught in a crash due to a brake failure. Raj reveals he may move back to India after his work hits a reef. Sheldon and Lucy meet and become friends. Title: Michael's car accident was caused by a brake failure.
S9E24 26 May: The Absency Formulisation. Leonard flies to New Jersey to see Michael. Penny receives an email from disney to be a part of Toy Story 4, which she knows Leonard will love. Raj and Howard find out Patrick Stewart is hosting a Star Trek tour and Wil invites them. After hearing of Bernadette's pregnancy, Sam Wolowitz goes to the Wolowitz house, but is too late to catch Howard, leaving him and Bernadette to discuss his absence. Shamy is left alone. Sheldon decides that he wants to marry Amy; at the same time, Amy wants that. They discuss their relationship before simultaneously proposing.