In this episode, while trying to find out what is making a mysterious sound, the Kratt brothers stumble upon a proboscis monkey troop, and after they bump into each other, the leader of the troop activates their Creature Power Suits and pushes them into the mud. But when the leader injures itself while saving one of its members from being eaten by a gharial crocodile, Martin finds himself as the new leader of its troop.
The episode begins with a live action segment. The Kratt brothers introduce primates with the cotton-topped tamarin. Afterwards, they ask their "What if?" question and the show transitions into the cartoon segment.
Aviva gives the Kratt brothers discs created with the DNA of an unknown animal, and after hearing a mysterious sound, the Kratt brothers swing through the canopy of the Bornean rain forest to find out the origin of the sound. Not long later, they find a proboscis monkey, which Martin names Schnozzle. After noticing the nose of the proboscis monkey in action, the Kratt brothers decide to find out what proboscis monkey noses are used for.
While brachiating across the trees with Schnozzle's troop, Martin names one of the monkeys Nosey. The Kratt brothers then decide to show off their climbing moves but crash into each other and fall onto a branch. Schnozzle activates their Creature Power Suits by stepping on the activation buttons and afterwards pushes them into a puddle of mud at the bottom of the tree. The Kratt brothers climb up the tree and find Schnozzle's troop. The female monkeys caress them, but Schnozzle, thinking that the Kratt brothers are taking over his troop, scares them away. The Kratt brothers are about to return to the Tortuga when they notice a gharial crocodile sneaking upon Nosey. Schozzle attempts to save him, but before doing so, he falls off a branch and injures himself. The Kratt brothers split up: Chris takes Schnozzle back to the Tortuga while Martin stays to make sure Schnozzle's troop is okay.
Martin first decides that the troop should eat leaves. He grabs a pile of leaves and eats them but spits the leaves out because they taste bad. He calls Chris, who is nearby with another proboscis monkey troop. The troop's leader challenges Martin to a fight over territory. Martin tries making a "kerhonk" with his nose. Although he does not come close, Martin is able to convince the leader that he is not worth fighting.
Chris continues to follow his troop. The leader makes an alarm call with its nose and gathers the troop members after noticing a clouded leopard nearby. Chris tells Martin to look out for predators and make an alarm call when danger approaches. While Martin practices making an alarm call, Nosey tickles Martin's nose with his tail. Martin successfully makes a "kerhonk", and consequently the members of his troop climb to higher ground right before a clouded leopard appears from the thickets. Chris then appears and tells Martin to take the troop to the river bank for safety reasons. Once they reach the river bank, however, the troop jumps into the river and swims away. The Kratt brothers think that they are deserting them. Martin jumps into the river and follows the troop. Chris sees a gharial crocodile entering the river. After helping the troop across the river, Martin makes a "kerhonk" and scares the crocodile away. Once they reach the other side of the river, they find Aviva and Schnozzle, who is now reunited with his troop.
The show transitions into the ending live action segment. The Kratt brothers describe the purpose of why some monkeys look unusual and do unusual things. Afterwards, they conclude the episode by saying "Keep on creature adventuring; we'll see you on the creature trail!"
- The proboscis monkey uses the sound made by its nose as a warning call and to communicate important information.
- Other than its nose, a proboscis monkey can also swim, and its four-chambered stomach allows it to eat leaves that are hard to eat.
- The ecological topic shown in the cartoon segment is herbalism.