Approximately four years ago, a new computer virus known as the Venjix Virus had infected all the computer systems and had taken over the world's communication, power and defense systems. Venjix built the Grinders, advanced robots and laid waste to the world. The dome city of Corinth was created as a safe haven by the military and it was not easy to enter it as Venjix's army made it difficult. A year ago, a defense group known as the Power Rangers RPM were formed. A mysterious vagabond, with no memory of his past, managed to enter Corinth, after it had been closed with the help of Ziggy, a mischievous fellow who has a tendency to get in trouble. The stranger, who calls himself Dillon has Venjix hardware grafted inside of him that gives him super abilities and because of his heroics, he is chosen to join the team.
Ziggy had to protect the Ranger Green powers and bonded with them so the powers wouldn't get in the possession of Tenaya 7, a powerful human-like minion of Venjix. When a part is needed for the Croc Carrier, the #6 zord with no need of an operator, the team's leader Scott must face his past and obtain the part. The Croc Carrier forms the ValveMax Megazord with the zords of Green and Black and the ValveMax combines with the High Octane Megazord to make the Zenith Megazord. Dr. K, who raised most of her life in a government facility with happy-go-lucky twins, remembered her past and her deep dark secret... that she released the Venjix virus. When Venjix's virus in Dillon was accelerated, the base code of the virus was needed and Dr. K used it, revealing to the Rangers she release the virus. The team forgave her even though Dillon harbored some anger about it.
In order to find out about his past, Summer hypnotizes Dillon and he finds a memory of a city outside Corinth. The Rangers head there and are interrupted by Venjix, in a robotic body and loose to him. They are then saved by two new flying zords. They realize the city is a trap and encounter the pilots of the zords, Ranger Gold and Ranger Silver. To the surprise of the Rangers when they return to their garage, Dr. K has a past relationship with the two Ranger Series Operators, she had thought they were dead. Gem and Gema tell the Rangers of a prison and Dillon believes he might have a sister there that the twins knew, revealed by the tune in his locket. The Rangers discover Venjix has slaves build a doom machine, Dr. K manage to manipulate it into a new zord that can combine with the twins' zords to make the Mach Megazord. Tensions between Dillon and Summer also grow high to the point that they almost kiss.
Gem and Gema have acting before thinking things through, leading to the Rangers having a stern talk with them and after getting a taste of their own medicine, they learn their lesson and vow to follow the rules. Tenaya goes digging in the old government facility Dr. K and the twins were held in and discover powerful abandoned zords. Colonel Truman and his team also discover video linking Dr. K to Venjix. Because only the Rangers knew the secret, Truman hadn't known but now he wanted to arrest her for treason. Dr. K cleverly alludes the soldiers and manages to save the day with the PaleoMax Megazord. She manages to convince Colonel Truman to let go the past and forgive her because she is trying make amends and stop Venjix. Venjix's most feared general, Kilobyte arrives and shakes Tenaya's confidence to the core and she sabotages General Shifter's newest robotic body for Venjix. Venjix banishes Shifter and Shifter fights the Rangers on his own and takes control of the PaleoMax.
Dillon finds his sister's key and because of a ceremony using two keys, it dons on him he can combine the keys and discovers a new tune in his locket... the tune Tenaya whistles most of the time. Dillon confronts Tenaya with the truth, she doesn't believe him until she bleeds and finds out the truth through the records of Venjix. To make amends, she uses Shifter's codes to take down his Hyperbot and the codes are also used in the union of the RPM Ultrazord, made of all twelve zords. Unfortunately, Tenaya is kidnapped by Kilobyte and reprogrammed as Tenaya 15, who no longer has an independent mind. Dillon has a difficult choice between reviving his sister and saving his friends when in danger and chooses the latter.
Later on, Venjix has Tenaya steal a device, which he uses to activate all his hidden Hybrids within Corinth. He takes over the control tower and trashes Dr. K's lab, taking her and Ziggy hostage. Venjix taps into the biofield and deletes Rangers Silver and Gold. Dillon resists the hybrid activation signal enough to inject himself with Dr. K's antidote. He saves Tenaya from Kilobyte, injects her, but he gets hit and ends up in a coma. The other Rangers convince Tenaya to go to the tower and hack into Venjix's system with a new virus. Dr. K bring back the twins, who blow the tower down. Dillon wakes up and rescues Tenaya, escaping the falling tower with a parachute. The tower falls right on top with Venjix, defeating him. After the defeat and the city recoups, Scott becomes leader of the Eagle squad; the twins join said squad; Flynn and his dad are in charge of the new systems; Ziggy and Dr. K form a school; and Dillon, Summer, and Tenaya roam the planet. The Rangers returned their morphers to Dr. K, the Venjix virus trapped within them, in a case locked away.