Today, Ash, Misty, and Brock encounter what seems like an impassable river. Seeing some workers nearby, Ash asks one of the men if there are any bridges to get across. He says that all the bridges were washed away from the typhoon last month, but fortunately, his construction crew should have the soonest bridge finished in only… six months!
Hovering overhead, James cooks a pair of potatoes using the furnace from Team Rocket's balloon. The impatient Jessie tells James to hurry, so Meowth suggests turning up the fire to make the potatoes finish faster. James complies, but the fire ends up burning the balloon, forcing Team Rocket into a crash landing in the forest.
Still distraught over the situation, our heroes spot an old man in his boat. They run up to the man, asking if he can give them a ride over the river. He agrees, but on one condition; Ash must capture a Sudowoodo first. Ash looks up Sudowoodo in his Pokédex, who mentions that the rare Pokémon likes to hide in trees to avoid capture. Knowing this, the gang sets off to find one. Eavesdropping on the conversation, Team Rocket plans to do the same thing.
Misty tells her Psyduck, who unexpectedly appears from its Pokéball, to help find Sudowoodo. Psyduck spots a Sudowoodo not too far away, so it runs back to its trainer, who doesn't notice the Pokémon in the distance. Taking a closer look, Misty finally notices it, and everyone gives chase. Sudowoodo runs off, but the gang goes in the wrong direction and loses it. They instead find two researchers arguing over something. The male researcher introduces himself as Pierre, and the female researcher introduces herself as Marie. Marie tells our heroes that she and her colleague are researching the Sudowoodo that live around the forest, and Pierre adds that he's trying to convince Marie that Sudowoodo are in actuality, Rock type Pokémon. Everyone is reluctant to believe this, since Rock Pokémon are usually rough and rocky, and Sudowoodo have more characteristics of a Grass type. Marie tells Pierre that finding out the truth firsthand is the best way to know what type it is, when suddenly, Brock holds Marie's hand and suggests that they should do some research in the field of love. As usual, Misty pulls him away by the ear, telling him that his position in that field is left out.
Using Noctowl to get a bird's-eye view of the area, Ash soon finds a Sudowoodo. He sends out Chikorita to attack, but Sudowoodo uses a "Vine Whip" on it. However, it turns out to be an ordinary vine from the forest. It then throws some leaves at Chikorita, and thinking that it's Razor Leaf, Ash finds that it's just a bunch of dried leaves. Ash commands Chikorita to use Vine Whip, but Sudowoodo counters with a real Vine Whip this time. This baffles everyone, so Marie tells Ash to use another Pokémon in hopes of Sudowoodo using another attack. He uses Totodile to try a Tackle, but it misses. Totodile then fires a Water Gun, but Sudowoodo frantically dodges it. As Totodile chases Sudowoodo to around the forest, Sudowoodo falls into a hole. It turns out to be the trap of Team Rocket, who are disguised as trees. After doing their motto, James tells Weezing to use Smokescreen. When the dust clears, the group finds Team Rocket has escaped with Sudowoodo.
Wondering if Sudowoodo is a Grass or a Rock Pokémon, Jessie and James tell Meowth to ask what type it really is. Sudowoodo replies, suggesting that they should get something to eat. Meowth asks again, and Sudowoodo says that it's the type it wants to eat. Annoyed, Jessie decides to forget about it, and to just bring Sudowoodo to the old man.
The old man notices that the Sudowoodo Team Rocket brought him is unhappy. Knowing that Grass Pokémon love being watered, James decides to shower Sudowoodo with his Squirtle watering can. Sudowoodo starts panicking and runs away, so Team Rocket chases it back into the forest. The man decides that maybe he can catch Sudowoodo by himself.
Meanwhile, the group finds Sudowoodo on a rock. It starts to run away again, but Brock tackles it and gives it some Pokéchow. Now happy and calm, Sudowoodo decides to cooperate.
Back at Marie and Pierre's lab, Marie tries to get Sudowoodo to use the Vine Whip it used earlier. It doesn't, so Ash has Pikachu shock Sudowoodo in order to give it some encouragement. Instead of a Vine Whip, however, Sudowoodo nearly shocks Pikachu back with an electric attack. Pierre discovers that Sudowoodo is using Mimic, and in order to prove that it's a Rock type, he begins to hose Sudowoodo down with water. Sudowoodo flees and jumps out of the lab window, only to run into Team Rocket again. The old man approaches as well, and explains that he's Marie's grandfather, and when he found out his granddaughter needed a Sudowoodo for research, he started asking everyone he met to find one for him.
Nevertheless, Team Rocket decides steal Sudowoodo. Jessie sounds out Arbok, and Ash chooses Cyndaquil. Arbok lunges itself at Cyndaquil to use a Tackle attack, but Sudowoodo grabs it by the tail and uses Slam. It then uses Faint Attack, followed by Low Kick, knocking Arbok out. As she brings out Wobbuffet, Jessie decides that with such sneaky and tricky attacks, Sudowoodo is the perfect Pokémon for Team Rocket. Ash tells Cyndaquil to use Flamethrower on Wobbuffet, but Sudowoodo is in the way, and spits flames back at Cyndaquil. Cyndaquil dodges and then tries to Tackle Wobbuffet, but it uses Counter and Cyndaquil bounces off. Coming up with an idea, Misty sends out Poliwhirl, and tells Ash to distract Wobbuffet. As Cyndaquil approaches, Poliwhirl surprises Wobbuffet from the side with a Water Gun, blowing Team Rocket away and blasting them off again!
Sudowoodo runs, but Marie decides to let it go, finally concluding that Sudowoodo is a Rock type. She and Pierre make up, telling each other that next time they should stick to the facts rather than focusing on winning an argument.
Marie's grandfather gets Ash and his friends across the river, while someplace else, Team Rocket climbs up a very steep cliff. Reaching the top, James grabs onto a branch, but it ends up being a Sudowoodo. Not being able to hold the weight of two people and a Meowth, the Sudowoodo lets go of James and Team Rocket falls down.