Ash and co. are in a forest and headed towards the Violet City gym. They come across a cluster of trees that are bare. Ash finds it weird on how the whole forest is green except for these trees. Brock says that the trees aren't burnt nor is it Fall, so it doesn't make sense. Pikachu spots something up ahead. On a tree are a few Heracross. Misty finds them creepy because of her fear of bug Pokémon. Ash looks up Heracross in his Pokédex. Ash wants to capture all the Heracross, thinking that will save the trees. A man behind them comes out. He tells Ash that he can capture the Heracross, but that might bring the forest more danger. The man introduces himself as Woodroffe, a ranger. Ash and co. introduce themselves too. Woodroffe explains to them that the Heracross help the Butterfree. They see the Butterfree eating the leftover sap from the trees. The Butterfree are too weak to dig into the trees, so they rely on the Heracross to start the sap flowing. Woodroffe then says that a group of invaders has been ruining the balance of the forest.

Pikachu senses something again. Up ahead is a bunch of charging Pinsir. Woodroffe says that the Pinsir are the invaders. All the Pinsir jump on the tree that the Heracross are on. They show off their sharp claws and scare the Butterfree away. Ash and Misty tell the Heracross to chase the Pinsir away. However, when the Heracross see the Pinsir's claws, they get scared and fly away. Misty wonders why the Heracross just flew away. Woodroffe tells her that the Heracross are too nice and peaceful. Brock concludes that all the trees will be destroyed if the Pinsir succeed. Then they see one Butterfree trapped in the tree. A Heracross seems to be trying to protect it. The gang of Pinsir begin to attack the lone Heracross. Ash sends out Bulbasaur. Bulbasaur uses Vine Whip which knocks all the Pinsir to the ground. Butterfree flies away, but Heracross is too exhausted to fly. The Pinsir get back up and they head for the tree again, but Pikachu uses Thunderbolt to fry them. The Pinsir regain conciousness, but this time they go for Pikachu. Finally, Pikachu uses Thunder, and the Pinsir run away.

Ash calls for Heracross. Heracross looks relieved, and it flies down. It walks up to Bulbasaur and Pikachu. Ash thinks that Heracross wants to thank them. Instead, Heracross begins to suck the pollen out of Bulbasaur's bulb. Bulbasaur gets angry and it hits Heracross with a Vine Whip. Misty thinks that Heracross was just hungry for more tree sap. Ash and co. think that the problem is solved, but Woodroffe tells them that the Pinsir will be coming back. He tells them that the Pinsir and Heracross used to live peacefully because they each had their own forest. For some reason, the Pinsir have been invading the Heracross's territory. Ash and Brock agree to help Woodroffe with the problem. So the group decides to head to the Pinsir forest.

On their way to the forest, Woodroffe says that the leaves can get pretty thick. Bulbasaur uses Razor Leaf to clear the path. Ash sees Heracross following them. He thinks that Heracross wants him to be his protector. Misty thinks that Heracross just wants to suck Bulbasaur's nectar again. Bulbasaur uses Razor Leaf on Heracross which scares it. Then the group walks on toward the forest. They come to a river. Woodroffe tells them that there is a rope bridge a few short steps up the river. They reach the rope bridge only to find it destroyed. Then they notice the Pinsir jumping on trees to get to the other side of the forest. Ash thinks the Pinsir cut the bridge themselves, but Woodroffe says that the ropes were cut by a human. The group sees Heracross again pushing a tree. Misty thinks that Heracross is being annoying by eating the sap. Brock thinks that Misty is wrong and that Heracross is trying to help them. Sure enough, Heracross pushes the tree over, and it creates a bridge for the group to use to get to the other side of the river. Ash, Brock, and Woodroffe walk across the fallen tree. Misty thinks that they are all crazy. Togepi slips out of Misty's arms and onto the bridge. Togepi plays around a bit and is about to fall when Misty catches it just in time. Then she also walks across the bridge to the other side. They see Heracross eating the sap from the tree.

Ash and co. notice that Heracross is still following them. Woodroffe tells the group to stay alert since they are almost at the Pinsir forest. Woodroffe then points to the tallest tree. That's where the Pinsir live. Ash and co. see a Pinsir in the tree that is bigger than its normal size. Woodroffe tells them that the Pinsir is actually a robot. Suddenly, Team Rocket comes out and they say their motto, then explain how they got the Pinsir robot:

Two days ago, Team Rocket was very tired and hungry. They had been hiking for hours and collapsed with exhaustion. Meowth smelt something good, so they rushed to the source. Finding a tree with sap, Jessie thought it looked disgusting. Meowth walked up to the tree and tasted the sap. He thought that it tasted good. Jessie and James then tried the sap, and they agreed that it was good. It gave Jessie the idea to open up a pancake restaurant.

However, Team Rocket knew that the restaurant wasn't such a great idea after all, so they just got a Pinsir robot to suck up all the sap which they could then sell. Brock now understands the situation: since Team Rocket was using up all the Pinsir's sap, the Pinsir went to the Heracross forest to look for food. Ash blames Team Rocket for the whole thing. Jessie sends out Lickitung and James releases Victreebel. Then James quickly runs in the forest to hide from Victreebel. James finds it strange how Victreebel didn't attack him. He sees Victreebel eating the sap and scolds it. This makes Victreebel attack James. Even Lickitung is busy eating the sap. Meowth gets out a remote to control the robot Pinsir. Ash sends out Bulbasaur. Bulbasaur uses Razor Leaf, but the robot Pinsir doesn't get damaged because of its steel body. Bulbasaur then uses Vine Whip by wrapping its vines around the robot Pinsir's body. It gives the robot a spin. Then Pikachu uses Thundershock, but the attack doesn't affect the robot Pinsir. The robot Pinsir absorbs the shock and sends it right back at Ash and co. The robot Pinsir begins to walk towards Ash and co., however Heracross comes out and blocks it. The robot Pinsir begins to push Heracross backwards. Using all of its strength, Heracross pushes the robot Pinsir backwards too. Then Ash and co. run to the robot Pinsir's sap tank. Meowth tries to fix the problem, but the remote is broken. Jessie grabs it off him, but James thinks he can fix it better, so they begin to fight. The remote tears apart. When Ash and co. get all the sap back, Heracross picks up the robot Pinsir and throws it at Team Rocket. The robot Pinsir explodes, and Team Rocket blasts off.

The Pinsir start to come back to their home now that Team Rocket is gone. Woodroffe tells the group that the Pokémon can now live in peace again. They see the Pinsir eating the sap again. On the other side, the Heracross and Butterfree share their sap. Heracross walks up to the group. Ash and co. congratulate it for doing a nice job. Ash and co. then say goodbye to Woodroffe and Heracross. As they continued walking, Ash and co. see Heracross following them. They wonder what Heracross could want. Brock thinks that Heracross wants go travel along with them. Ash throws a Pokéball at Heracross and captures it. Then they continue their journey to Violet City.

English Official Summary

Ash and friends discover a forest where invading Pinsir are causing heavy deforestation. Investigation reveals the root of the problem: Team Rocket is carelessly harvesting sap from a nearby woods, thereby upsetting the balance of nature.