Someone has been swiping fish off Cap'n Turbot's boat, so he calls Ryder and the PAW Patrol to help investigate. Using his new spy gear, Chase inspects the boat and heads below deck where he discovers it's a group of pesky penguins! Now the pups have to catch the slippery suspects and find a way to get them back to the South Pole!
The episode begins with Cap'n Turbot on a new, larger version of the Flounder, when Wally appears and performs a trick the Captain deems worthy of a fish. However, when the Captain goes to check his bait bucket, it's empty. Wally whimpers at not getting a fish, but the Captain remembers he just got in a fresh shipment of frozen fish in, but like the bucket, when he opens the crate, all that's inside is the ice cubes that kept the fish cold. Having one other option left, the Captain decides to share his tuna fish sandwich, but while he still has his attention focused on Wally, his lunch bag is snatched off the bench by an unseen figure. Wally does a face-palm, and when the Captain slips on the ice cubes, but manages to dive perfectly into the water, Wally gives him a score of 2.5 for it, before planting a fish on Turbot's head.
At the Lookout, Skye is bouncing on her trampoline, while Marshall is enjoying the swing. Chase is practicing his super spy skills when he looses his footing and falls onto the swing, joining Marshall for a bit before Marshall swings him free and he bounces across the grass.
Elsewhere, Ryder is on his ATV, returning to the Lookout, when Cap'n Turbot calls, requesting his help regarding the fish vanishing from the Flounder. Ryder says that the PAW Patrol will do their best, then summons the pups. Marshall loses control of himself on the swing, is sent flying, bounces off Skye's trampoline, then crashes into Chase, sending both police and fire pups tumbling into the elevator, and into the other pups, smacking them against the inside of the elevator. After Marshall says excitedly how much he loves group wipeouts, the pups are taken upstairs, Chase being suited up in his super spy gear instead of his regular police uniform. Once topside, Ryder briefs the pups, then requests Chase and Zuma's help for the mission: Chase for his super spy skills, Zuma for investigating the waters around Seal Island and the Flounder.
The team deploys, Chase's pup house having been converted to its super spy version for deployment, and as they reach where Ryder and Zuma take to the water, Chase is ordered to eject from his truck, landing safely on the back of Ryder's ATV, and together, they head for Seal Island.
By the time they get there, it is already evening. Ryder has brought some fish-shaped pup snacks to find the thief, but while distracted, one of the treats is taken right under their noses. Chase immediately starts investigating for the thief, noticing a scent he's never smelled before. He activates his "wall walkers" to climb up to the top of the Flounder and continues to sniff, having a little trouble when a seagull sets off his allergies when several feathers fall on his nose. While he continues to check the Flounder, Ryder and Zuma head underwater with another treat, but while they look in one direction, a black flipper snatches the treat away in the other, leaving Ryder and Zuma even more puzzled.
Night soon falls, and with Wally and Cap'n Turbot asleep, Chase engages his night-vision goggles to look for the thief, spotting a trail of footprints that lead into the hold. When he follows them, his night-vision spots a figure in the back, and he tackles it. Ryder and Turbot arrive to see what he found, but all Chase found was Turbot's old inflatable ducky, Driftwood Ducky. Ryder decides to set a trap to lure the thief out, and soon, with the bucket loaded with the remaining treats left out on deck, the thief reveals itself: a penguin. Chase tries to apprehend it, but it is too smart, and even reveals there are more of them. Chase relays the news to Ryder, Zuma, and Cap'n Turbot, and they get topside immediately to help, save Cap'n Turbot, who wants to take pictures of them. The penguins prove to be too smart and slippery for the PAW Patrol, and any attempt the Captain makes to take their pictures is ruined by bad timing, or his own excitement.
As the team regroups to figure out how the penguins got up north to Adventure Bay, and how to round them up, Wally soon reveals how the penguins got north in the first place: an iceberg! Now that the iceberg was next to the Flounder, there was just the matter of luring the penguins back onto it so they can be taken home to Antarctica. Fresh out of treats, the Captain realizes he still has his freeze-dried squid jerky, perfect for luring the penguins back onto the iceberg. Despite the stinky smell of the jerky, it works. When Zuma pulls the bucket full of the jerky after his hovercraft via his buoy, the penguins, currently underwater to avoid being caught, take the bait, and follow Zuma all the way back to the iceberg, where Zuma leaves the bucket, and the penguins dig in happily.
One mission accomplished, now they just had to figure out how to get the iceberg back to Antarctica ASAP. Luckily, Ryder has Cap'n Turbot check his lighthouse logs for any ships heading south, and a freighter just happens to be en route to the southern tip of South America.
The next morning, the Flounder is towing the iceberg towards the freighter so it can be anchored to the ship and the penguins can be taken home, but the PAW Patrol enjoys what time they have left with the penguins to have some fun belly-sliding like them. The episode ends as Cap'n Turbot and Wally are having their picture taken with the penguins, only for it to be ruined when Marshall crashes into them, leaving the final picture showing everyone being scattered as a result of Marshall.