In another dimension, the RPM Rangers are the last hope. After a brief showdown against the Skyrev Megazord, Professor Cog escapes the battle.

In a subway, Professor Cog and his group of Grinders make the scene. In the city, the Samurai Rangers arrive to face Sharkjaw. Gold Ranger joins the fight. Professor Cog watches as the Samurai Rangers struggle against the Nighlok. Gold Ranger takes on Sharkjaw with his Barracuda Blade. Professor Cog watches as the Nighlok retreat. Master Xandred has General Gut and a large group of Moogers ready for battle.

Back in the city, Professor Cog enters the Netherworld to meet Master Xandred. Professor Cog wants to use some of the Sanzu River to poison the humans. He orders Master Xandred to prepare his army. Master Xandred agrees to the plan. Back in the subway, the Red Ranger makes his appearance. The Rangers celebrate their victory with ice cream. A car lands right in front of them. The Red Ranger grabs a piece out of the car. The Rangers run into the swarm of Grinders. They morph into action and begin the battle. They find the Grinders to be a challenge. The Red RPM Ranger joins the battle. He shows the Rangers how to defeat the Grinders. The Rangers demorph and meet Ranger Red. He tells them that their weapons are too weak to defeat the Grinders. Kevin doesn't want to trust Ranger Red. Ranger Red impressed the girls. They bring him to the Shiba House. Ranger Red doesn't morph because he can't breathe the air. He follows up about living in a dome. Back at the Sanzu River, Master Xandred tells Professor Cog to help the Nighlok. The Grinders make their attack on Antonio.

Antonio morphs into action and fights the Grinders. Back at the Shiba House, Ranger Red explores the house while the Rangers eat their dinner. The Gap Sensor alerts the Rangers to battle. Mia is upset about her meal. Ranger Red takes Master Ji's bike. Ranger Red summons his Street Sabre and helps the Gold Ranger, who assumes that Jayden has a new helmet. The Samurai Rangers and the robotic villain make the scene. Professor Cog uses his turbine attack to blast the Rangers on the feet. Red Ranger starts to respect Ranger Red. Professor Cog follows up with a Portal attack, that can send the Rangers into his dimension. The Rangers protect the Red Rangers from the portal attack.

Jayden and Ranger Red head out of the lake. Jayden tries to help Ranger Red, who gives him the cold shoulder. Ranger Red is not easily impressed with Jayden's title. Jayden is worried about his friends, but Scott tells him that the RPM Rangers will help them. Back at the Sanzu River, the Grinders start collecting the Sanzu River. At the Shiba House, Jayden and Ranger Red meet up with Mentor Ji. Jayden morphs into action and summons the horse. Ranger Red takes the bike again. Both Rangers race to the scene. Red Ranger beats Ranger Red in the race and is very upset about his lost. Professor Cog reveals his plot: The Red Rangers battle each other. The Red Rangers battle in an epic sword fight. The Red Rangers fire their best attacks to each other. Mentor Ji's plan to reverse the poison worked. The Rangers were staging the fight to fool Professor Cog. The Red Rangers work together to fight the villains. Red Ranger summons a car for Ranger Red. Ranger Red gives the Nitro Blaster to Red Ranger for a brief attack. They turn their attention to Professor Cog. Ranger Red and Red Ranger power up to Shark Attack and Super modes. The Rangers return to join the fight and defeat Professor Cog. They turn their attention to the Mooger army.

The Samurai Rangers summon the war houses and head towards the Mooger army. The Rangers work together to trim down the army size. Red Ranger faces off against General Gut, who insults his sword. Red Ranger reveals the Fire Smasher and begins the sword fight. After a brief battle, General Gut knocks Red Ranger to the ground and prepares to finish him off.

As General Gut is about to finish off Red Ranger, Red Ranger reveals the Shark Disc and transforms into the Shark Attack Ranger. He uses the new Shark Sword to defeat the swarm of Moogers. The Rangers work together to defeat General Gut. The Nighlok grows into his large form. The Rangers summon the Megazord, who is immediately defeated. The Red Ranger summons the Shark Zord to defeat General Gut's serpent. The Rangers form the Samurai Shark Megazord. The new formation defeats the Nighlok for good. Gold Ranger helps Ranger Red fix the car. Back at the Sanzu River, Master Xandred is disappointed with the failure. Back at the subway, Scott says goodbye to his new friend. Mike wants Red Ranger to demorph to say thanks. He tells Mike good luck with Emily. Ranger Red heads back home. The Rangers head for home for Mia's cooking. Mike notices as Emily turns around and smiles at him.