One year after the previous film, while at the Corny's family restaurant, the Heffley family - consists of Greg, Rodrick, Frank, Susan and Manny - plans to attend Meemaw's 90th birthday. However, after Greg and Rowley rescue his younger brother Manny, who got stuck inside a tube in the play area, Greg ends up in a ball pit with a diaper stuck on his hand, startling him. He subsequently becomes famous after the people around him record him and post the footage on the internet, leading Greg to be dubbed as "Diaper Hands", much to Greg's devastation. Later, at the Heffley residence, Greg learns that Player Expo is taking place not very far from Meemaw's house in Indianapolis. Greg's gaming star, Mac Digby, will be attending, and Greg hopes to meet him and get in one of his videos so he will gain newfound popularity..