Ryder and the pups travel into the jungle in the PAW Patroller with great excitement. Chase then reveals that they were visiting the jungle once again to celebrate Carlos' birthday. Shortly after, they arrive at their destination with Carlos and Tracker waving at them. Ryder greets Carlos with a "happy birthday" and the pups back with "gracias, mis amigos".
Ryder then surprises Carlos with the giant cake the team had brought, with Carlos saying that his favourite flavour was "giant" jokingly, making all the pups laugh. Rubble then quotes that he almost forgot how beautiful the jungle was but Rocky suddenly felt that something seemed missing. He soon suggests party decorations to be put up and Robo-Dog appears from the PAW Patroller, pushing out a cart filled with Balloons and Streamers to aid the pups in decorating. Tracker volunteers to put up the Streamers with his cables, hanging them all over the jungle trees, with Marshall and Skye praising him for his cool moves. Tracker then remains on the tree and looked as if he was looking out for something. When Zuma asks him what he was looking out for, he swings down and walks towards the pups, replying that he was just looking out for Mr. Mailman whom was to deliver his secret birthday gift package to Carlos. Rubble insists to reveal the gift to the other pups, but Tracker declines to make it a surprise for everyone. Carlos overhears this and says that he is grateful about Tracker's thoughtfulness but mentions that he did not need a gift as he was already happy that everyone was in the jungle to celebrate his birthday. Skye and the other pups then reassure Tracker that the gift would be delivered on time.
Meanwhile, Mr. Mailman drives his delivery truck through the jungle. He quotes that he should be driving more carefully after going through a bump on the jungle road, to prevent his mail from being delayed. Soon after, he goes through another bump.
As Mr. Mailman traveled, Rocky is seen using his claw to inflate a pink balloon and he passes it to Skye, whom uses her pup-pack to fly to a nearby branch to tie the balloons on. Tracker continues to put up the streamers using his cables. Soon after, a few mischievous monkeys begin taking down the balloons to their amusement. Ryder is amazed by all the streamers put up by Tracker and Tracker says a thank you, but when Rocky asks Ryder how he likes the balloons he and Skye put up, it bewilders Marshall who was close behind, and Ryder jokes with hesitation that the balloons were invisible, making Tracker, Rocky and Skye look up and also shocked of the missing balloons. Ryder quotes that the wind could have carried them away and reassures the pups that he brought extra balloons. Soon after, the sound of an inflating balloon could be heard. Tracker jumps out surprised and says that it sounded like screeching tires. With Chase assuming that it was Mr. Mailman's truck, the pups and Ryder all run towards the sound source with excitement. To their disbelief, it was only the monkeys monkeying around with the stolen balloons, solving the mystery, but it leaves Tracker worried about Mr. Mailman not arriving yet.
As they wait, Mr. Mailman continues driving his delivery truck through the jungle. He is seen avoiding some rocky obstacles but it causes his truck to swerve and hit a rock, causing the back of his truck to open, his sack of mail and Tracker's package to fly out onto a tree branch and his truck to spin, ending up in a mud pit. He shortly calls Ryder.
As a balloon escapes the tank it was attached to while Ryder was inflating it, he picks up Mr. Mailman's call and summons the pups to the PAW Patroller. The pups all head towards the Paw Patroller with the usual Marshall shenanigans and Ryder briefs them on their mission. He deploys Chase to use his vehicle's winch to pull the truck out of the mud and Tracker to use his pup-pack's cables to bring down the mail from the tree.
When Ryder, Chase and Tracker reach the site, Tracker realizes that the mud the truck was stuck in was in fact quicksand. Chase is successful in pulling the truck out of the quicksand with Ryder's guidance. Meanwhile, Ryder asks Tracker to bring down the mailbag from the tree branch. Tracker extends his cables and brings the bag down, but notices that his package for Carlos was not inside. However, Chase notices something left up on the branch and it was indeed Tracker's package. Tracker once again extends his cables out to retrieve it, but was taken away by one of the monkeys via balloon before Tracker got hold onto the branch. He is shocked by the event while Mr. Mailman quotes that "He has heard of Airmail, but never before Monkey Mail." Ryder offers to help Tracker get back his package, but mentions that it would be hard to track it down through the dense jungle. However, Tracker suggests that he could just simply listen out for it with his ears. Chase, bewildered, asks how could he listen for it when packages couldn't make sounds but is answered by Tracker confidently that his package does do so. He soon picks up its sound with his ears and begins leading the chase.
Meanwhile, two monkeys pass the package between each other atop a branch but one misses the catch, causing it to tumble down into the clutches of a snake, which moves to another tree. Tracker gets to the monkeys, asking about the package but does not get an answer. He continues the search with his ears and cables. He misses the package being held on the snake, but soon realizes it was behind him after swinging onward and goes back towards the snake. However, a red jungle frog hops on it instead and rides on it down the jungle trail as if it were a surfboard. Tracker asks the snake about the package, but the snake just leaves, annoyed (probably by the frog). The frog then slides down onto the road where Ryder and Chase were riding their vehicles but they completely miss it when Tracker calls them up from behind. The frog continues downward but barely escapes a rock flinging the package into a gorge. Chase asks Tracker whether he found his package with Tracker replying a sad no, but he mentions the package could still be heard, just that it sounded more like an echo. Ryder checks his pup-pad map and finds that a gorge was up ahead of them, concluding that if the package had fallen into the gorge, it would have made the sounds coming from the package sound more like an echo. Ryder and the pups then start moving towards the gorge in hopes of finding the package.
When they reach the gorge, the package stood on the edge of a wooden rope bridge. Tracker jumps off his jeep and starts running up towards the package on the bridge jubilantly. But out of the blue came one of the monkeys who stole the package, attempting to grab the package, but it fails, resulting in the package dropping down into the gorge and landing on a rock stilt. Ryder suggests that they all go down the gorge to retrieve it but Tracker replies that it would not be possible as the cliff hills (the sides of the gorge) were too steep. Ryder then suggests that Tracker uses his cables to retrieve it from the bridge by lowering himself in. Tracker agrees with the idea and goes on to lower himself down. However, to his dismay, his cables were too short and he relays it to Ryder. Ryder receives the message and deploys in Skye for air support. A few moments later, Skye is seen using her helicopter's grabber to grab onto one of Tracker's cables to lower him down to the package. He misses once but soon gets it. Ryder praises Chase, Tracker and Skye and they all return back to the celebration. When everyone was back, Carlos and Tracker extend their gratitude to the pups and Ryder. Ryder then quotes his usual phrase, with Rubble adding on saying, "Or yelp for cake" in context to the episode and him being impatient to get a bite of cake. However, he is paused by Tracker who mentions that Carlos should be opening his present first. Carlos opens his present and to his surprise, was a picture frame with a photo of him and Tracker. Carlos commends Tracker but Tracker adds on by clicking onto a button on the frame, which started playing a tune where he sang his Happy, Happy Birthday song to Carlos. The other pups also dance along.
When Tracker is finished, Carlos gives him a big warm hug, making the other pups awe in a sweet manner. Ryder then asks everyone on cake, with Rubble hungrily replying that he didn't need to be reminded twice. But a monkey (the one that stole the package) instead swoops in and steals the slice of cake Ryder was holding on to, making Tracker add on to Rubble's comment that the monkeys didn't need any reminders for cake.