Location: Amazon River

Featured animals: Red-Bellied Piranha, Redeye Piranha, Silver Dollar, Red-Bellied Pacu, Altum Angelfish, Arapaima, Ripsaw catfish, Payara, Golden Dorado, Sabalo, Giant River Otter, Red-tailed Catfish, Freshwater Stingrays, Yellow-Spotted Amazon River Turtle, and an assortment of tropical fish species

Villain of the week: Zach Varmitech

Animal names: Razor Wind (for the entire shoal of red-bellied piranhas, not an individual)

The Wild Kratts are heading to the Amazon River to study red-bellied piranhas. But before they do that, Martin has something to discuss the team about.

"Okay guys, so we've faced a lot of bad guys in the past," said Martin, "some of which we know very well. But the new ones, though, are something different. And because there are so many, I decided to give them codenames so that we can address them fast," he then pulls up pictures of all the villains the team has encountered with one picture still black with a shadowy figure, "so we have Zach, the cry baby…"

"The cry baby?" said Chris, "But he invents, just like Aviva. Can't we just call him the Inventor?"

"Naw, I like cry baby better," said Aviva, "It fits him well."

Martin continues, "…next, we have Donita, the Fashion Designer, Gourmand, the Bad Chef, Phil Han, the Stuffer, Marcus Marionette, the Pet-Collector, Cheng Dajin, the Medicine Man, and finally, our Mystery Man."

"Hmm, mystery man?" said Koki.

"Because we still don't know who he really is," said Martin, "All we know is that he's still at large and we must stop no matter what it takes."

"It's good what you're doing," said Chris, "but we have a mission to do."

"Right, to uncover the truth behind the misunderstood piranha," said Martin who pulls out clips of piranhas.

Aviva, Koki, and Jimmy got a little freaked out from looking at the clips.

"Are you guy okay?" Martin asked.

"Why are studying those?" Aviva asked.

"Haven't you seen those horror movies!?" Jimmy panicking, "They'll tear you to shreds!"

"No, you guys have it all wrong," said Chris, "Piranhas are just misunderstood creatures that we don't know much about."

"And to prove it, we'll go swimming with them," said Martin.

The team reacts in shock and terror.

"Are you serious!?" Koki asked, "Are you seriously gonna swim with fish that can devour you to the bone!?"

"We can prove to you the piranhas are not what they seem," said Martin.

"I agree," said Brandon, "Piranhas are not the vicious fish we see on public television. There is a truth behind these fish.

"Oh, babe," said Aviva, "I love you so much, but there's no way I can believe that. I mean, you saw how fast they can eat a carcass. And you guys are gonna swim with those same fish that ate a whole chicken in seconds?"

Both the Kratt brothers and Brandon replied "Yup!"

"Well then, good luck to you all we are here on the Amazon River," said Jimmy who landed the Tortuga on a bank next to the Amazon River. The Kratt brothers and Brandon put on their wetsuits to go swimming in the river.

"Be careful, babe," said Aviva.

"I'll be fine, Aviva," said Brandon who gives her a kiss.

"Don't worry, Aviva, he'll be fine with us," said Chris.

"Yeah," said Martin.

"That's what I'm afraid of, but just in case" said Aviva as she hands to Brandon chainmail, similar to the Vikings, "Now then, each of you guys have a camera attached to you so that we can catch the action on the piranhas. If you can prove to us that piranhas are not the monsters we thought they were, then we'll be sold."

"Alright!" they shouted as they run into the river.

"You know, this kinda reminds of that time back with the Nile Crocodiles," said Koki, "You used to not like them but after learning about them, you appreciate them more."

"Maybe this is the same as so," said Jimmy.

"Only one way to find out," said Aviva.

Meanwhile, Zach was eavesdropping on them, hearing about the piranhas.

"Hmm, piranhas, ehh," said Zach, "If I can harness their powers, I can use them to tear apart more than just flesh. I can shred buildings, bridges, and maybe even the Tortuga. Alright Zachbots, I want you to go fish."

The Zachbots pull out a deck of cards and play go fish.

"No no no! I don't mean the card game, I meant spy on Chris, Martin, and the ninja underwater to view the piranhas!" said Zach all furious and frustrated.

The Zachbots enter the river and start following the Kratt brothers.

"Wow, the Amazon river is so alive," said Martin swimming around with shoals fish, stingrays, and turtles.

"Yeah, I'll say," said Chris, "it's like an underwater highway."

"Do any of you see the piranhas?" Brandon asked while looking around.

"No, but I see a golden dorado swimming right above us," said Martin pointing at a 6-foot long golden dorado swimming above.

"It looks like it's hunting that shoal of sabalo," said Chris.

"That's it! When the dorado catches its prey, the leftovers from the kill should attract the piranhas," said Brandon.

"Great idea!" said Martin, "Now we just wait."

The dorado darts into the shoal of sabalos, catching one in the process. Bits of the fish drop and the shoal of red-bellied piranhas arrive to the scene.

"Oh, and here they come," said Martin as the piranhas begin their feeding frenzy. All that was left was bones.

"See, I told you they're vicious monsters," said Aviva watching the action from inside the Tortuga, "I think you guys should leave before they make a meal out of you guys."

"But the quest only just got started, now we need to follow them," said Chris.

"Did he just say 'follow' the shoal of vicious, man-eating fish?" said Koki.

"Oh come on, they're not man-eaters," said Martin, "They don't really attack everything that's in sight.

"Like that one fish coming towards you?" said Aviva as a red-bellied fish comes near Martin.

Martin nearly panics but on closer inspection, the fish turned out to be a red-bellied pacu.

"Oh, haha, it's only a red-bellied pacu," said Martin.

"Pacu?" said Aviva.

"Oh yeah, they're actually related to the piranhas, but are vegetarians. This one was after a berry that fell on top of me," said Martin.

"A relative of the vicious, mean predator that's a vegetarian? How weird," said Aviva.

"Oh yeah, and check this out: Silver dollars," said Chris with a shoal of silver dollars.

"Did someone say silver dollars!?" said Jimmy all excited, "We're gonna be rich!?"

"Hahaha, no Jimmy," said Chris, "Not the money, I meant the fish. These are also related to the piranhas but are also herbivores."

"Ha, I see where you're going," said Aviva, "but they're not piranhas. They're just related to them. So that won't work."

Suddenly, a large fish pops out and attacks one of the silver dollars.

"Whoa, did you see that, Chris?" Martin asked in awe.

"Oh yeah, looks like a piranha attack, to me," said Chris as he swims closer to the large piranha.

"I told you, red-bellied piranhas are vicious killers," said Aviva, "you better get out of there before its friends come out and shred you to pieces."

Chris takes a close look at the piranha, "Actually, he doesn't have friends."

"Huh, why's that?" Aviva asked.

"Because he's a black piranha," said Chris.

"A black piranha?" said Koki, "So there's a Red piranha and a black piranha?"

"Well, Koki, the black piranha is larger than the red-bellied piranhas but are usually solitary," said Chris, "so you won't see this one with friends."

"But that shoal of piranhas will come in any minute to eat the leftovers," said Aviva all worried.

"Actually, the entire shoal is over there where the angelfish are," said Brandon pointing at the shoal of red-bellied piranhas encircling a couple of altum angelfishes. The angelfishes seemed to be injured and were trying to swim away, but the piranhas attacked them at an instant

"Now that's what I call a feeding frenzy," said Martin.

"Guys! They're killing those fish! Don't you see how vicious they really are!?" said Aviva all frantic.

"Those angelfishes looked pretty beat up," said Chris, "they must've been attacked by a large, predatory fish and escaped. But something triggered those piranhas to go into frenzy mode."

"It's kinda like those great white or tiger sharks," said Brandon, "All it takes is a drop of blood and they instantly go insane."

"Oh boy, do not remind me of that," said Martin.

"That's it!" said Chris.

"What's it?" said Aviva through the communicator.

"Blood," said Chris, "Maybe it was the blood those angelfishes were giving off that got the piranhas into a frenzy."

"So they're blood thirsty monsters?" said Aviva.

"Aww, don't keep doubting them," said Chris, "there's still much we haven't discovered, yet."

"I'm serious! The last thing I want is to see you all get shredded into pieces by fish underwater!" said Aviva who was all worried and upset.

"Aviva, babe," said Brandon, "It'll be alright, I promise."

"Alright!" said Martin, "I think I'll name it Razor Wind!"

"Huh?" said Chris, "which one is Razor Wind?"

"All of them," said Martin.

"How can they all be Razor Wind?" Chris asked.

"Well, they're fast when it comes to devouring their food and they have razor sharp teeth," said Martin.

All of the sudden, a large fish darts into the shoal of piranhas.

"Whoa, did you see that!?" said Martin.

"I saw that, and it was fast," said Chris.

"Overthere!" said Brandon pointing at the Arapaima eating a piranha.

"Whoa, an arapaima, one of the largest freshwater fish in the Amazon River," said Martin.

"Those fish are like living torpedoes," said Chris, "darting at fast speeds to catch its prey, like catfish or, in this case, piranhas."

"Wow, a creature that hunts those nasty monsters," said Koki, "Now that's my kind of fish."

The shoal of piranhas swim to the bottom to avoid the arapaima but one of them gets sucked up by a red-tailed catfish.

"Whoa, that catfish just gobbled the piranha in one gulp," said Martin.

"I never thought these vicious killers would have so many predators," said Aviva, "I guess I feel a little sorry for these guys. But they're still scary and I think I should invent a creature power that will definitely keep the guys safe from the piranhas."

Then, a family of giant otters appears into the water, encircling the piranhas and picking out individuals.

"Wow, look at them go," said Martin.

"Amazing, giant otters can hunt piranhas by simply grouping up on them," said Chris, "It's like they're using the piranhas' tactic against them."

"That's it!" said Aviva, "I'll make giant otter powers for the Kratts to combat those snapping monsters."

"Somehow, I feel like this is déjà vu," said Koki.

"Come to think of it, it almost seems to be exactly like the time we were with those Nile crocodiles," said Jimmy.

"Man, those otters can sure go fishing for some deadly fish," said Martin.

"Look, those piranhas are swimming off," said Chris.

"But where?" asked Martin.

"Shall we follow them?" asked Brandon.

"Let's do it," said Chris leading the way.

Meanwhile, back at Zach's private jet, Zach is building some robots that will house the red-bellied piranhas.

"Hehehe," said Zach who's watching the monitor while building his robotic piranhas.

Back with the Wild Kratts, the piranhas start to split off.

"Huh?" Martin wondered, "Why did they split off like that?"

"Don't you remember, Martin?" said Chris, "Red-bellied piranhas aren't exactly shoal fish. They just simply tolerate each other."

"Wait a minute," said Aviva through the Creature pod, "are you saying they just happen to hang around each other?"

"Now that I find hard to believe," said Koki also speaking through the Creature pod, "Everytime I see those nasty fish, they're always hunting in packs, just like wolves."

"Right, but that's because it is how the social media portrayed them as," said Chris, "but in reality, they just hang around together looking for food."

"Chris, look," said Brandon pointing at one of the piranhas.

"Where is that one going?" Chris wondered and swam to get a closer look.

"Aww man, now I have to rename them all individually," said Martin all disappointed.

"Martin! Brandon! Check this out!" said Chris.

Martin and Brandon swim up to Chris to see a piranha with a clutch of eggs.

"I don't believe my mind, it must be a male," said Martin.

"Hmm, a ferocious piranha is actually guarding a nest of eggs?" said Koki all surprised.

"Not just him, look," said Chris as he points out to the same piranha he was following.

"So that one has to be a female, then," said Brandon.

"Wait, hold on, so piranhas are also caring parents?" said Aviva.

"Yup, just like I said before, déjà vu," said Jimmy.

"Maybe we should really reconsider our views toward the so-called vicious piranha," said Koki.

"But they can still attack the bros and my hubby at any moment," said Aviva who's still working on her creature power disks, "once I finish making the Giant river otter disks, the bros will be able to swim with those monsters with greater ease."

"But we just verified that these fish don't really attack unless something provokes them like the smell of blood or fresh meat of some kind," said Koki, "and those two piranhas are parents trying to protect their young. They would only mean harm if something were to try to get to their eggs."

Far from shore, Zach assembles his army of Zachbots.

"Alright Zachbots, time for you guys to catch me some fish," said Zach holding up a picture of a red-bellied piranha, "I want you to catch this particular piranha and ONLY this one! Now go fish!"

The Zachbots thought he meant the card game and pulled out a deck of cards to play go fish.

"No you idiots! Not the card game go fish, I meant get in the lake and find as many of this fish as possible!" said Zach all annoyed.

The Zachbots move into the water and start collecting the red-bellied piranhas. As the gather some, they drop the piranhas into individual piranha robots that tap into the piranha's brain to receive only their instinct to go on a feeding frenzy.

Back with the bros, Chris sees everything and calls Aviva.

"Aviva, this is a real emergency," said Chris, "I saw Zachbots stealing piranhas!"

"Zachbots?" said Aviva, "Are you sure? Zach is supposed to be in prison."

"He's not kidding on this one," said Brandon as they watch the Zachbots take the pair of piranhas guarding their eggs.

"Aviva, this is bad," said Martin, "Not only did Zach escape from prison and stole all the piranhas, but if those don't get protected, they'll get eaten up! You have to build for me a piranha suit!"

"But I never wanted to," said Aviva, "I didn't think it would come down to an emergency like this."

"Well it's now or never," said Chris, "I'll take the giant otter disk to search for Zach whiles you, Ninja, head back to the Tortuga to help the guys out."

"On it," said Brandon as he swims back to the Tortuga.

Back at the Tortuga…

"Oh no, is this really happening?" said Aviva, "If only I wasn't too judgmental these piranhas I would've done something to help them."

"I should be taking the blame, too," said Koki, "If I wasn't too focused on those piranhas I would've found out about Zach being nearby."

Brandon enters the Tortuga, "Aviva, is everything alright?"

"No," said Aviva, "I just finished making the river otter disk but haven't even started the piranha disk for Martin to use!"

"Jimmy and I can help you with that," said Brandon.

"I just need to modify the largemouth bass disk to feature piranha powers," said Aviva as she tosses the giant river otter disk to the teleporter, "Jimmy heads up!"

The disk reaches the machine and Jimmy teleports the disk to Chris.

"It's outta here," said Jimmy.

"Okay, now onto the piranha disk," said Aviva.

Brandon pulls out a picture of a diagnostic of a piranha, "So piranhas are known for their jaws that have razor sharp teeth, but there's another ability of the piranha's jaw. Their jaws can extend out, which helps with grabbing food and tearing of pieces of flesh."

"Got it, razor sharp teeth and extendable jaws," said Aviva as she modifies the bass power disk.

"So why are the piranhas needed in the Amazon?" Jimmy asked.

"Red-bellied piranhas are mostly scavengers, which helps clean the rivers of carrion," said Brandon, "Without the piranhas, the river would be polluted with detritus and not a lot of creatures can live in it as a result."

"So piranhas are not scary monsters after all, then," said Koki.

"Done!" said Aviva who finished making the piranha creature power disk, "Jimmy, send this to Martin.

Aviva chucks the disk to the transporter and Jimmy zaps it away.

"It's outta here!" said Jimmy.

Back with the Kratt brothers, the giant otter disk reaches Chris.

"Okay Martin, I'll go see if I can put a stop to Zach while you protect those eggs," said Chris who then goes after one of the otters to touch and then shout, "Activate Creature Power Suit!"

Chris turns into a humanoid version of a giant otter and swims down the river with the rest of the family group toward Zach's location.

"Good luck Chris," said Martin as a piranha disk appears next to him, "And just in time!"

Martin inserts the disk into his creature power suit and touches one of the eggs, shouting "Activate Creature Power Suit!" to turn into a humanoid version of a piranha.

"Wow, so cool," said Martin, "I have fast twitching and reflexes! Not to mention a strong sense of smell."

A ripsaw catfish arrives to the scene, going straight after the eggs.

"Oh no you don't, catfish!" said Martin as he fends of the catfish, only to attract a school or red-bellied pacu, "Uh-oh, this could be a real challenge."

Back at the Tortuga…

"Guys, I'm picking up a weird reading and it's coming right towards us!" said Koki looking at the monitor.

"They look like flying robotic fish," said Jimmy.

"They are," said Aviva, "Zach is mind-controlling the poor fish and utilizing only their feeding frenzy behavior."

Zach appears on the monitor.

"Ahahaha!" Zach laughed maniacally, "Well, well, well. Like my new invention? I call it the Piranha-bots and their sole purpose is to shred whatever I want to be shredded, and I'm gonna use your Tortuga as a test subject to see if my bots succeed or not!"

"Shouldn't you be in prison?" said Aviva all mad, "How did you escape!?"

"Huh, like I care to tell you," Zach responded, "But the titanium teeth from my Piranha-bots will definitely make short work of your greatest invention! Ahahahaha!"

"I'll go deflect as many of the robots as I can," said Brandon grabbing one of Aviva's inventions: a pair of Gecko feet shoes, "The rest of you need to help gather the remaining piranhas to quarantine them until free of Zach's mind-control."

"That is if Chris stops him in time," said Jimmy as they head out to the Tortuga.

Outside the Tortuga, a huge swarm of flying, robotic piranhas powered by the red-bellied piranhas themselves head towards the Tortuga. Brandon readies himself by pulling out his swords while the others gather some buckets of water to transport the fish to the quarantine tank.

"Here they come, Ninja," said Aviva as the swarm closes in, "Try not to hurt the fish."

"Got it," said Brandon as he began fighting off the piranha bots with his swords on the Tortuga.

Every time Brandon knocks of a robot, the piranha gets moved into a quarantine tank by one of the Wild Kratt crewmembers.

"Hanging in there, Ninja?" said Koki transporting the fallen piranhas.

"Just fine," said Brandon trying to keep the Piranha-bots off the Tortuga using his shurikens and kunais.

Meanwhile, Zach is watching from a safe distance.

"Hahaha, soon they'll be overwhelmed and those Wild Rats will be done FOREVER!" said Zach.

"Hold it there, Zach!" said Chris, "Those piranhas belong back to where they live. Without piranhas, the rivers would've became very polluted with carrion which would make the water unsafe for fish to swim in and for the creatures to drink. They play a role in the river like vultures in the African savannah, so they're misunderstood for their terrible reputation."

"Oh boo you!" said Zach, "I will rule the world with Piranha-bots and I will get every last piranha in the river to build my army! Zachbots! Get him!"

Some Zachbots go after Chris.

"You asked for it," said Chris as he begins to vocalize, summoning the entire family of giant otters to attack the Zachbots.

"Ahh! Get those doggy-thingys away from me!" said Zach all terrified.

"They called otters, Zach. Giant otters," said Chris as he picks up a master controller, "Is this the control for those Piranha-bots?"

"Hey! Give that back!" said Zach as he goes after Chris for the remote controller, but Chris was quick and jumped back into the river.

Chris makes it back to the Tortuga with the remote control, "Aviva, this is the control for those Piranha-bots!"

Aviva receives the remote control, "I'll just press the turn off button and the fish will be free to go!" Aviva presses a button and the Piranha-bots shut down, releasing the fishes.

"Alright, we did it!" said Koki.

"You said it," said Brandon all exhausted from preventing the Tortuga from getting chewed up.

"Now we just have to release all the piranhas back to where they belong, living free and in the wild," said Aviva.

Zach's private jet flies over them, shouting "Argh! This isn't over yet, Wild Rats! I'll get you all someday!" and then flying off.

"That's Wild Kratts to you," said Chris.

Back in the river, Martin struggles to fend off the pacus until the parents returned to defend their nest.

"Whew, now that's a close one," said Martin, "keep up the good work."

The team regroups outside the Tortuga.

"Boy I sure learned a lot about red-bellied piranhas," said Aviva, "like how their bad reputation isn't entirely true to begin with."

"You got that right," said Koki, "From now on I will see piranhas in a different view perspective."

"Yup, the only real monster we saw today was none other than Zach," said Jimmy.

"And the important thing is that they now live free and in the wild," said Chris.

"And I still need to name them all," said Martin looking out the river, "Ninja, did I name that piranha, yet?"

"I don't know if that's the same one you named or not," said Brandon trying to take notes.

Everyone else laughed.