At the Lookout, the pups are making sure their vehicles are looking nice and shiny for Alex Porter as he is having a big party for the kids and pups at his grandfather's café, with Marshall helping out with decorations.
Meanwhile, at the café, Mr. Porter and Alex are working the decorations when they point out the big part of the party, that being the piñata. However, Mayor Humdinger is passing by with the Kitten Catastrophe Crew when he overhears the Porters, and has Cat Skye aid him with stealing the piñata to get at the treasure inside when the Porters are not looking. When the Porters discover it, Alex is devastated, and Mr. Porter calls the pups to tell them of the situation.
Ryder assures the Porters they will get the piñata back and finish the decorations and summons the pups. Marshall crashes into the elevator with his decorations, but the pups laugh it off as they head topside for their orders. Chase, in his Super Spy gear, will help Ryder locate the piñata, while Marshall assists the Porters in finishing the decorations. The team deploys and heads out, with the sirens on Chase and Marshall's vehicles wailing long, loud, and proud.
Once they reach the café, Ryder discovers Humdinger in the background of the photograph Mr. Porter took of Alex next to the piñata before it was stolen, thus leading Ryder and Chase back to the Catastrophe Crew's hideout in Foggy Bottom, where they call out Humdinger to return the piñata. Humdinger tries to keep quiet to avoid drawing suspicion, but once Chase has his drone confirm the piñata is with Humdinger and the kittens, he asks for it back, but Humdinger and the Catastrophe Crew make a run for it, kicking up a cloud of sand to blind Ryder and Chase as a means to buy them time to escape.
Meanwhile, Marshall gets right to work helping Mr. Porter with the decorations, and after a small accident, which results in the rest of the decorations being set up perfectly, everything is ready for the party.
Back with Chase and Ryder, they give pursuit of Humdinger, who has the Catastrophe Crew try to block Ryder and Chase's pursuit, starting with Cat Rocky and Cat Rubble causing a rockslide, but Ryder and Chase maneuver around the rocks, then Humdinger has Cat Chase and Cat Zuma attempt to stretch a rubber band across the road to send Ryder and Chase backwards, but that misfires, then Cat Skye drops a pair of balloons loaded with oil to slip up Ryder and Chase, but while Ryder converts his ATV to hovercraft mode to drive over the oil, Chase manages to maneuver his truck around it. Soon, Humdinger finds his way blocked by a canyon, and when the Catastrophe Crew tries to open the piñata again, he tries to get it away from them, sending him back down the canyon on the carrier as Ryder and Chase arrive. Ryder calls Skye in to save Humdinger with her harness just as the carrier flies off into a tree, but Humdinger refuses to abscond with the piñata until he gets it open, only for another attempt with it to cause him to slip and drop the piñata, which Chase saves with his zipline.
Back at the party, Alex thanks the PAW Patrol for saving the piñata, but when Humdinger complains that the piñata can't be opened after the effort he and the Catastrophe Crew put into it, Alex reveals that the piñata is designed to be opened when someone pulls the right ribbon on the bottom of it. Alex pulls the right ribbon, causing the prizes inside to fall out, and Humdinger asks for something from it as a means to make up for all the trouble he had with it today. However, Mr. Porter reveals that the so-called "cookie" that he tried to eat was a pup treat for the PAW Patrol as thanks for all their help. Disappointed, Humdinger decides to leave with the kittens, but Alex offers him a toy car that was in the piñata as a gift to remember the party by. Humdinger is grateful for Alex's gift, especially since the car was purple, his favorite color, and thanks him, before the party gets underway as Humdinger and the kittens take part as well from the sidewalk.