At the Lookout, the pups have recently made homemade wind chimes using recycled glass bottles. They soon bring one to Mayor Goodway and it impresses her greatly. The pups then point out a painting of one of her relatives, making her go into detail about the treasure of golden bones that could be hidden underneath Adventure Bay.
However, after they head into the next room, Mayor Humdinger and his Kitten Catastrophe Crew, who overheard everything, decide to go hunting for the treasure. Heading into the underground tunnels in a large driller, Humdinger begins drilling between the underground tunnels in an attempt to find the room where the bones are hidden. However, as he continues to come up empty-handed, his actions begin to affect Adventure Bay above. Among the problems include the sidewalk outside Katie's Pet Parlor cracking open, the melons on Mr. Porter's fruit stands tumbling out of their displays, the park bench where Ms. Marjorie and Maynard were sitting on, where it flips over and traps Maynard as the shaking was reported to Mayor Goodway by Ms. Marjorie and the statue of Chickaletta where it begins to sink upon Ms. Marjorie's report. This causes the Mayor to call Ryder.
Once Ryder gets the call, he summons the pups to the Lookout for an Ultimate Rescue mission. As the pups head up after Marshall's usual shenanigans, the PAW Patrol shield changes to show Rocky's badge, and the pups are suited up in repairman uniforms. Ryder also sports one as he reveals that their Ultimate Rescue will have Rocky as the team leader. With that, Rocky heads down to his truck and are both lowered into the underground maintenance area for it to be upgraded into its Ultimate Rescue appearance, which looks like a combination of a street sweeper and tow truck. Once the rest of the pups load up, and Ryder emerges from his garage on his repainted ATV, now sporting green paintwork, the team heads off on their mission.
Once at City Hall, Rocky deploys the mini-construction vehicles from his Ultimate Rescue truck to lift the statue out of the hole, deploy a barrel inside as a stable base, and have Marshall then add in foam to keep the barrel in place, so when Skye lowers the statue back down, it is balanced and stable. Afterwards, hearing the rumbling from Humdinger's drilling again, Rocky takes Chase, Zuma, and Rubble with him to the underground tunnels while Skye and Marshall continue the repair work above ground.
Finding the holes that Humdinger drilled, along with tons of scrap metal, Rocky salvages the metal, while they continue their search.
Meanwhile, Humdinger finally locates the hidden room where all the golden bones are, but in his haste and greed to grab them and escape, he takes out the pillars that, ironically, are keeping Adventure Bay City Hall above ground. causing it to sink, threatening to crush Humdinger and his Catastrophe Crew while they are busy grabbing the bones.
When Ryder and Rocky arrive, Humdinger attempts to escape with his loot, but wedges his drill bit into a wall, and realizing the danger afterwards, panics, and ends up breaking the drill bit off his vehicle. However, Rocky is able to use it, along with the scrap metal from Humdinger's earlier drilling, to make a temporary scissor-lift to keep City Hall from sinking. However, realizing they need a more stable set of pillars to keep the building from sinking again, the decision is made to use the golden bones as the new pillars. With Skye and Marshall arriving shortly afterwards, the pups are able to stack the bones like Jenga towers to provide more stable pillars for City Hall.
As for Humdinger and his kittens, they are punished with sealing off the room with a wall of cinder blocks to ensure no one ever sets foot in it again, much to their chagrin. Back above ground, Rocky is commended for a job well done by Mayor Goodway, and everyone shares a laugh afterwards regarding their latest Ultimate Rescue mission.