Greg’s parents finally find out about Rodrick’s party. When Mr. Heffley looks through photos from Thanksgiving, he finds a photo that a partygoer accidentally took with Mrs. Heffley’s camera. Rodrick tries to deny the truth, but Mr. and Mrs. Heffley ground him for a month, and they punish Greg by revoking his video game privileges for two weeks because he helped Rodrick. Mr. and Mrs. Heffley decide to go out of town again, but since they no longer trust Greg or Rodrick, they leave Manny with Gramma and send Greg and Rodrick to stay with Grandpa at his condo, Leisure Towers. Greg complains that there’s nothing fun to do at their Grandpa’s and that Grandpa’s TV is always tuned to the security camera in the front lobby of the building. Greg must eat Grandpa’s terrible watercress salad, and they play Grandpa’s old board games that don’t make any sense to Greg.

Back at home, Rodrick has a big Science Fair project coming up, and Mr. and Mrs. Heffley refuse to help him. Greg remembers how last year Rodrick didn’t finish his Science Fair project about horror movies and whether or not they cause viewers to produce violent drawings, and the whole family got involved to draw pictures and help him out the night before the project was due.