It started at Jake's mountain in Adventure Bay in the evening, Rubble was building an observatory with some help from construction workers. That night was the big night, a comet was coming for everyone to see. Once the building is done, Rubble installed the big telescope inside. Mayor Humdinger and the Kitten Catastrophe Crew arrived to see what's going on. Mayor Goodway and Cap'n Turbot were explaining that a comet is coming, and says the one who sees it first gets to name it. Everyone in Adventure Bay's gonna see it, and there was a big screen inside the observatory that's hooked up to the telescope, that way everyone will see the comet together. Mayor Humdinger wanted to see the comet first and name after himself, but of course, he needed a telescope to do that. He came up with a plan to steal the observatory.
The observatory was done, the comet would appear at midnight tonight, so the PAW Patrol went back to the Lookout for a quick nap. The PAW Patrol started napping at the Lookout, as Everest and Jake were napping at their cabin. And for that, Mayor Humdinger had finally got the chance to steal the observatory. He and his kittens installed wheels and a turbo booster onto the building to make it move to Foggy Bottom. Humdinger went inside to see the telescope and told his kittens to not start the booster until they were ready. But, Cat Rocky turned it on and let the observatory move. The kittens caught up and got themselves stuck in the building with the mayor inside. Now, the observatory was in big trouble.
Everest and Jake heard a noise outside their cabin and discovered the observatory out site. At Uncle Otis' cabin he was feeding beavers at the pond with vegetables. But, what didn't noticed is that the observatory wrecked down his cabin. As he saw the rubble, he started to call the PAW Patrol. At the Lookout, Ryder got Otis' call about his cabin wrecked down, then Everest and Jake's about the observatory missing. It was a big job of construction, but Ryder knew that he and his pups would do all of that. He summons the pups to the Lookout for an Ultimate Rescue. Once the pups entered the elevator and got into the changing room, the PAW Patrol badge had change into Rubble's tag. The pups were wearing construction gear, and the Lookout lights were yellow. Ryder told the pups about Otis's cabin and the missing observatory. This is an Ultimate Construction Rescue, Rubble was going to be the team leader for this rescue, while the other pups follow along. As Ryder slides down the pole, Rubble went down the slide to his rig. But instead of a regular vehicle transformation, Rubble's pup-house lowered down to the maintenance room, and it turned into an Ultimate Construction Truck, with a big scoop, a big dumper, a steamroller, a drill, and a shovel with a hook. As it raised up to the surface, the other pups hopped on and drove off, as Ryder was driving his ATV painted in Rubble's texture. And, off they go to do some construction building in Adventure Bay.
Once the PAW Patrol arrived at Uncle Otis' cabin, they started to get to work. Rubble was clearing the debris with the ultimate truck scoop, while Marshall uses the steamroller to flatten the ground. Zuma used the drill to make mini holes for the posts. Chase used his winch to put up the walls with help from Marshall and Zuma. Then, Rocky used his hammer to hammer everything together, so the cabin doesn't fall apart. After the cabin was finally rebuilt, Ryder was wondering what wreck it in the first place.
For Mayor Humdinger and his kittens, they were still riding the observatory, moving out of control. It was stopped by a big rock, and it blocked the door, the mayor and kittens wouldn't get out. After pushing it, the observatory started to move again. At Otis' cabin, Rocky discovered a door knob from the observatory, they think the observatory was there. Chase started looking for clues with his flashlight, and he found tire tracks. Rubble believed the observatory had wheels to move around, the PAW Patrol continue searching. They'd reach the observatory and started to catch. Skye began to fly on construction copter on her pup-pack to see where it was heading now. The observatory was heading for the bridge, it's too heavy for it to hold. Luckily, Rubble caught up for Marshall to use his cement sprayer to spray cement at the building's wheels to stop it. It won't hold for long, Rubble and the other pups had to make a detour.
Once they arrived at the bridge, they began to be a curved wall for the observatory to turn and get away from getting on the bridge. Zuma drilled some holes, Rocky let down some posts, Ryder puts the posts in the holes, Rubble puts the girders in place, and Rocky rivet them. The observatory started to go again, since the cement cracked apart from the wheels. It bumped into the wall, hit a bumpy sand pile, and rolled towards town. The PAW Patrol started to go after it again. Mayor Humdinger had found another way to get out of the observatory. He started to climb the telescope, but made it the extend longer. And, because of that, the telescope hit the lemonade stand's cup, it was about to fall. Luckily, Rubble caught it on time and placed it back on the roof.
At City Hall, Mayor Goodway and Chickaletta woke up just in time for the come tonight. But then, the observatory came by, knocked the Chickaletta statue to fly, and bumped the City Hall bell tower. The PAW Patrol made on time to catch and place back the statue. The tower fell off the roof with Chickaletta trapped inside. Rocky got her free, and the PAW Patrol continued chasing the observatory. The observatory was heading for Farmer Al's farm; the PAW Patrol took a shortcut to get there first. At the farm, Farmers Yumi an Al saw a mother piglet with her new triplet piglets. The PAW Patrol arrived in time to warn them. They couldn't get the newborn piglets out of the way, and the team can't make another detour. As they saw an old shack, Rubble came with idea to use the roof as a ramp so the observatory won't crush the barn. The observatory was closer, Rubble used a wrecking ball to wreck down the shack, then used his scoop to move the roof in front of the barn. As the observatory arrives, the ramp made it drive over the barn without any damage. As it landed, the turbo booster fell out and turned off.
The observatory was rescued and placed back at Jake's mountain. Now, the comet show go on. Everyone saw the comet soaring in the night sky. Everyone was the first to see it, but to honor Rubble, they named the comet after him and his crew, the Construction Crew Cosmic Comet.