It's Friendship Day in Adventure Bay, and at the Lookout, the pups and Ryder are busy getting their friendship letters together to deliver to all their friends in the city. As they do, they sing a song about friends.
Later, Marshall and Rubble bring their letters to the Adventure Bay Post Office for the mailman to deliver, but soon Mayor Humdinger and Cat Chase arrive. Mayor Humdinger has Cat Chase give his friendship letters to the mailman, but Cat Chase purposefully shoots them so fast at the mailman that he falls over and twists his ankle, rendering him unable to deliver the letters. When Humdinger gloats about it afterwards, an argument breaks out between him and Mayor Goodway, resulting in Humdinger challenging Goodway to a friend-off, where whichever town can deliver the best Friendship Day gift to the other town will win. With that, Humdinger and Cat Chase return to Foggy Bottom to work on their gifts, while Goodway calls Ryder to let him know of how the mailman needs the PAW Patrol's help. Ryder lets her know the pups are on their way and summons them to the Lookout. Once topside, Ryder reveals that the entire team is needed to deliver the letters and the team deploys to help.
Once they reach the mailman, as they load up the letters, Goodway reveals her gift to Humdinger being a stack of all of Mr. Porter's cakes from his shop. With that, the team sets off to make their deliveries.
Zuma handles visiting Cap'n Turbot, Wally, and the whales.
Skye makes deliveries to Garbie, Mr. Porter, Jake, and Everest.
Marshall handles the north and south sides of town.
Rocky stays with Ryder.
Chase is tasked with delivering the cakes to Foggy Bottom.
Unfortunately, Cat Chase sees what the pups are up to and returns to Foggy Bottom to tell Humdinger, who's gifts for Adventure Bay are balloon baskets full of candy that the Catastrophe Crew were putting together since once Adventure Bay's citizens' teeth are full of cavities, they'll have to come to Foggy Bottom as that's where all the dentists are. When Cat Chase tells Humdinger of the gift Chase is delivering, while Humdinger leaves the rest of the Catastrophe Crew to finish the gifts, he and Cat Chase go to stop Chase before he reaches their town.
Unknown to Humdinger, the kittens decide to feast on the candy at Cat Marshall's suggestion, leaving the baskets unguarded, allowing some bunnies to climb into the baskets to nibble on the candy, then on the anchoring ropes, sending the baskets into the air, which is only noticed by the kittens when several pieces of candy fall to the ground around them.
Back with Chase, Humdinger has Cat Chase fire some thumb tacks onto the road to puncture and deflate the tires on Chase's patrol truck. As Chase struggles with the steering, the cakes are thrown off-balance and splatter on him. With the gift ruined and his truck incapacitated, Chase calls Ryder to let him know, and Ryder and Rocky head over to help him out.
Meanwhile, Marshall is delivering a letter to Little Hootie, but finds his nest next to a spooky house Rubble told him about earlier. Marshall wants to get Hootie's letter delivered and get out of there ASAP, but is so scared that when Hootie startles him, the letters land in the spooky house's yard, though Hootie still gets his. Marshall calls Ryder to let him know, and Ryder sends Rubble to assist Marshall. Rubble arrives to help, but just before they can retrieve the letters, they are yanked inside the house by the creepy critter that crawls around the yard, forcing Marshall and Rubble to nervously knock on the door and hope that whoever is inside will be kind enough to return the letters.
Back in Foggy Bottom, Humdinger discovers what's happened to the baskets, and when Cat Chase tries to chase one of the bunnies off, he ends up being carried away in the last basket, leaving Humdinger to reprimand the other kittens, who just look at each other with puzzled looks.
It is not long before Skye calls Ryder to tell him of the baskets now floating into Adventure Bay, and while Ryder has Skye try to direct the balloons towards his position using her helicopter, he has Chase deploy his net in a spot where, once he pops the balloons with his tennis ball cannon, the baskets will fall safely onto the net, leaving the bunnies unharmed. Goodway arrives to find the cakes ruined, but Rocky quickly gets to work fixing them with his spatula. Skye then spots two over the bay, one of them being the one Cat Chase is in, and with Zuma being given help from the mother whale and baby whale, Cat Chase and the baskets are retrieved, while Ryder and Goodway travel to Foggy Bottom to confront Humdinger.
Humdinger, knowing he's busted, tries to save face by offering a balloon bouquet to Goodway, since that's what he and the kittens were doing after the candy baskets idea backfired, but when he sees no gift from Goodway, he claims victory in the friend-off, only to find upon seeing Rocky's effort at fixing the cakes, redesigning them into a life-sized cake statue of Humdinger himself, to be on the verge of tears at how handsome it looks, before shooing off the Catastrophe Crew when they start licking it. However, trying to avoid admitting defeat, Humdinger grabs the whole lot of balloons, but the combined helium in all of them causes him to be lifted into the air, and Goodway, in a show of good faith and friendship to Humdinger, tries to pull him back down, only to be carried away with him while Chickaletta and the Catastrophe Crew look on, dumb-founded.
Back with Marshall and Rubble, when the door opens, they are met by the kindly Ms. Marjorie, who realizes that the letters she retrieved were not all for her, and reveals the creepy critter running around her yard to be her raccoon, Maynard, who has a habit of making her raise her voice at him to get him to behave. Before she can returns the letters, Maynard runs off with them, forcing Marshall and Rubble to chase after them to get them back.
Back in Foggy Bottom, Ryder has Skye try to navigate the mayors back to where Chase can try to get them down with his tennis ball cannon, but he pops too many balloons, sending the mayors careening back towards Adventure Bay, where they are able to spook Maynard back into Ms. Marjorie's arms, while Marshall is then able to retrieve the letters with his ladder.
While airborne, Humdinger was surprised at how Goodway tried to help him, and when Goodway explains that's what friends do for each other, it seems to convince Humdinger to begin repenting for all of his deceitful and dishonest moves he's made against Adventure Bay in the past, even going so far as to call Goodway his friend as well.
As Marshall and Rubble prepare to finish delivering the letters, they feel sorry for Ms. Marjorie, so Ryder works out a compromise in having Ms. Marjorie deliver the letters while riding on his ATV, while Maynard rides with Marshall in his firetruck.
At the end, the PAW Patrol lead all of their friends, new and old, including Humdinger and the Catastrophe Crew, in a reprisal of their song from the beginning of the episode in front of Adventure Bay City Hall.