Returning to Earth's moon after seeing to other conquests in his empire, the evil rule, Lord Zedd is displeased with Rita's failure to conquer Earth and destroy the Power Rangers. Imprisoning Rita and jetisoning her into space, Zedd creates new putties and a new monster that immobilizes the Dinozords.
Further problems arise for the Rangers when Zedd is able to take control of both the Tyrannosaurus Dinozord and the Dragonzord using them to wreak havoc. In order to combat the new threat of Zedd, Zordon and Alpha unveil the more powerful Thunderzords. But first the Rangers must regain control of the Dinozords from Pirantishead.
Thanks to the device created by Billy, the Rangers are able to regain control of the Dinozords, but Lord Zedd has other plans and uses his power to open a chasm in the earth that swallows the Dinozords. Tommy is able to return Dragonzord to the sea before Zedd claims it too. Fortunately, Zordon and Alpha are able to salvage the Dinozords and using the Power of Thunder, transform them into the Thunderzords. Using the new zords the Rangers take down Pirantishead at last.
During a period of galactic imbalance, Zordon must temporarily shut down, leaving Alpha 5 in charge. Wanting to help out, Alpha scans the Viewing Globe and sees a little boy named Dylan and teleports to the park to help him. Zedd taking advantage of the situation sends Primator to attack Alpha and Dylan. Alpha panics and orders Dylan to run while he activates his self-destruct sequence. The rangers are forced to take on Primator first instead of helping Alpha who only has minutes left. Primator proves a challenge as he's able to shape-shift and takes on the appearance of the rangers to confuse them. After being given a clue by the restored Zordon, the rangers exploit Primator's weakness and rescue Alpha in the nick of time.
Zedd causes his trouble with his newest plan to put division between the rangers. He uses his powers to cause Billy and Zack to see their friends in a new light as Putties. With the Rangers distracted, Zedd begins a new assault on Angel Grove with the Saliguana
Angel Grove High's Club Sign-Up Day brings up feelings up disappointment and jealousy in Kimberly when everyone seems to sign up for Trini's club and not her's. Zedd takes advantage of the situation and casts a spell on Kimberly to turn Kimberly against Trini. Kimberly is then caught by Zedd's newst monster, the Bloom of Doom who traps her in a mysterious dimension. Trini comes to her friend's rescue and break's the spell and as a team, the Rangers take down the Bloom of Doom.
A recurring dream about losing his powers troubles Tommy. What he doesn't know is that Zedd is reponsible for his nightmares. Zedd wants to capture Tommy and use him to steal the Sword of Power. After gaining it, Zedd's newest monster, Robogoat takes on Tommy, as he loses his powers, his nightmare starting to become reality. Coming to Tommy's aid, the Rangers are able to retrieve the Sword of Power and defeat Robo Goat.
Wanting to clean up Angel Grove, the Rangers lead a movement to do so, but Lord Zedd enacts of plans of his own with the Octophantom. Zedd plans to have Octophantom trap the Rangers in a jar and drain them of their powers. Taking advantage of Octophantom's vanity, Billy creates a mirrored device and Jason and Billy use it to free their friends and destroy Octophantom.
After agreeing to play for Ernie in a Broomball Tournament against the Stone Canyon Beetles, Zedd creates the Stag Beetle monster to challenge the rangers. Zedd plans to use Stag Beetle to drain Tommy of his powers and succeeds in doing it. Fortunately with the aid of a device created by Alpha, Tommy is able to regain his power and the others are able to take down the monster with the Thunder Megazord.
In his latest plan to defeat the Rangers, Zedd has Trini's neighbor Haley captured and is holding her for ransom. The cost: The Green Ranger. The Rangers must make it to Venus Island and rescue Haley before it sinks to the depths and Haley is lost forever to Zedd's evil world. With his powers failing, Tommy and Trini help free the captured rangers from the Invenusable Fly Trap. Defeating the monster, the rangers then rescue Haley right before she is turned evil.
Kimberly takes a shot at song-writing and gives Zedd the idea to create a little music of his own. Using his powers he turns a saccata on Bulk's shoulder into the Guitardo monster who wields Kimberly's guitar as a hypnotic weapon. Kimberly and Tommy realizes that music is the key to breaking Guitardo's spell and defeat the monster once and for all.
A peaceful day is ruined by a vision that Tommy receives of himself from the future bearing a message. Meanwhile Zedd has a plan to put an end to the Green Ranger once and for all. He'll use the Turbanshell monster to drain Tommy of his powers and use them to charge the Green Crystal. Turbanshell fights the Thunder Megazord and causes the Rangers to eject. Turbanshell then teleports Green Ranger to himself to finish draining his owers. With the Green Ranger Powers in hand, Zedd traps the other rangers in another dimension. With the Green Crystal, Zedd also puts an inpenetrable shield around the Command Center and unveils his Dark Rangers.
Zedd, telling the Rangers that without their will be nothing they can do to stop Turbanshell, teleports them back to the park. Meanwhile, taunting Tommy over the loss of his power, Goldar gets outsmarted and Tommy escapes. Breaking through the energy barrier, Billy makes contact with the Command Center and Zordon informs them that the Green Crystal must be destroyed. A powerless Tommy is able to get in undetected and destroys the Green Crystal restoring the Rangers' powers.. The Rangers call for the Thunder Megazord, but Turbanshell proves too much again. Tommy goes inside Turbanshell to deliver a heat wave while Zack chills him down with water. Weakened by the attack, the Rangers are finally able to take him down with the Thunder Megazord.
Jason feels guilty for not retrieving the Green Candle and saving Tommy's powers. In order to cheer him up, the other Rangers decide to surprise Jason by bringing Tommy home. Goldar surprises them though and captures Zack, Billy, Trini, and Kimberly and takes them to another dimension. Using the stump of the Green Candle, Goldar lights a Black, Blue, Yellow, and Pink candle to drain the rangers of their powers as well. Jason must save the rangers and their powers before the candles burn out. But first he must get through Zedd's Pipebrain monster and Goldar.
Needing a trumpet so he can play in the Jazz Festival, Zack offers his cousin Curtis their uncle's trumpet, a family keepsake. Billy, Zack and Kimberly are attacked by Putties in the park while on the way to the Youth Center. After distracting the teens to tamper with the trumpet unseen, the putties are destroyed. Everything seems fine until the tampered trumpet puts the teens under a hallucination spell. Zedd then turns the trumpet into his Trumpet Top monster. With the hallucination spell the Rangers are under, Trumpet Top brings back past monsters to fight and tire the Rangers. In order to break the spell, they must destroy Trumpet Top.
Still feeling victorious in the end of the Green Ranger, Lord Zedd sets eyes on Kimberly as his new queen. Sending Goldar to capture the Pink Ranger and place her under a spell, it's up to Billy and Trini to save their friend. Meanwhile, Curtis and Richie are attacked by Z Putties in the park, and it's up to Zack to come to their aid, splitting the team up even further. When Zedd sends his Mirror Maniac, made from a mirror gift to Kim, from Tommy, the Rangers regroup and finish the monster off with the Thunder Megazord and the saber.
With news of Tommy returning, the rangers make plans for a surprise party to welcome him back and with things "safe and secure in Angel Grove," Zordon and Alpha begin work on a secret mission. Zedd makes plans of his own though: Capture Tommy and make him evil again. But first he creates Nimrod, the Scarlet Sentinel to take care of the Power Rangers. After growing, Nimrod overpowers the Thunder Megazord with help from her assistants, AC and DC. Billy teleports to the Command Center to get help, and discovers the hidden chamber and Zordon and Alpha's mission: creating a new ranger! Meanwhile, Bulk and Skull try in vain to open up Rita's dumpster which has crash landed on Earth.
Billy regroups with the other rangers, who have retreated from battle, at his lab and reveals his discovery. The other rangers are not happy, and believe that Tommy should recieve these new powers. After a long wait, the rangers are summoned to the Command Center where Zordon and Alpha reveal their secret: The White Ranger is Tommy! Forced the split up, Tommy takes on Nimrod with his new Tigerzord while Zack, Kimberly, and Jason go to retrieve Rita's dumpster from Bulk and Skull. Billy and Trini must repair the zords after their battle with Nimrod. With the zords repaired and reconfigured, Tigerzord combines with the Thunder Assault Team to create the Mega Tigerzord which quickly defeats Nimrod, AC, and DC. With the monster destroyed, the rangers visit Bulk and Skull and send Rita's dumpster back into orbit.