In ancient Egypt, an evil sorcerer named Scarab, kills the pharaoh's son, Prince Rapses, so he can become immortal. Entombed alive for his crime, Scarab revives in the modern world and begins his search for Rapses' reincarnation.
Scarab sends a pack of animal spirits after Presley, who is out camping with his mom. Scarab discovers that an approaching eclipse is the key to using the boy to gain immortality. Set and Anubis first seen. All four struggle with first 'modern life' encounters.
Scarab invokes the earth spirit Geb to help defeat the mummies and grab the boy in time for the eclipse. They get Ja-Kal and demand Presley give himself up or Ja-Kal will die. Presley goes, and the eclipse nears, but he and the other mummies foil Scarab.
Nefertina frustrated by lack of respect, falls in love with a charming biker who in truth is the snake demon APEP, and is looking to take revenge on the family of the boy prince. Apep becomes a dashing rebel biker, and falls in love with Nefertina.
While Scarab yearns to be younger, Presley yearns to be older, to win an eighth-grade girl's heart. Scarab invokes the water spirit, Nuhn, to find the fountain of youth and all four Mummies must rescue Presley.
An amnesiac Rath must swallow his haughty pride and depend on the kindness of homeless strangers to survive until the mummies can find him. Meanwhile, Scarab is draining the years out of the homeless in order to add them onto his own life.
When imperious, cat goddess Bastet appears, Nefertina and all city cats are driven crazy. Bastet is furious that cats are no longer worshipped. Nefertina abandons the others to be with cat goddess Bastet.
The Mummies are forced to team with Scarab to defeat raging goddess Sekhmet. She has unleashed various plagues on San Francisco because modern society's failure to respect her. It falls to Rath to trust in his own 'mortal' abilities to outwit Sekhmet and save them all.
A girl in Presley's journalism class is sure something mysterious is going on with him. Like a crack investigative reporter, she tracks his every move. While the Mummies are forced to deal with a deadly Scarab plot, Presley must keep his inquisitive classmate from finding out about him, and he must protect her life at the same time.
The apparent return of Pharaoh Amenhotep I surprises and thrills Presley and the Mummies -- except for Ja-Kal, who has his suspicions. Vulnerable Presley is delighted at the chance to learn more about Rapses' real father while Ja-Kal feels threatened. Ultimately they uncover the truth it's a plot by Scarab.
When Scarab focuses all the powers of his magic at Rapses, in the hopes of obtaining the Spirit of Pharaoh, an explosive separation occurs instead. When the smoke clears, Presley finds himself in 1525BC Egypt, being attended to by princely servants, while the personality of Rapses, with all of its royal pretensions, finds himself in the body of a 20th century American seventh grader. The Mummies have to get things back to normal before the haughty prince gives them all away to Scarab. All four Mummies must reverse the separation of Presley/Rapses.
Scarab locates and raises the remains of a sunken ship containing Egyptian artifacts on its own artificial island. Presley falls into a trance-like state and heads off for the island. The Mummies follow, and Rath learns that if Presley looks at a magic mirror in the cargo then Scarab will obtain his Spirit of the Pharaoh. The Mummies must confront Set and Anubis, who were raised with the wreckage and now work for Scarab.
Scarab gets Chantra to turn herself into an appealing girl to lure Presley to him. But Chantra, overhearing what Scarab plans to get from Presley (eternal youth), decides to keep it for herself. All four Mummies are ordered by Presley to protect his mum Amanda, but must also rescue Presley from Scarab and Chantra.
Nefertina becomes a famous fashion model after she is 'dusted' with special 'diamond powder' Scarab had intended for himself. He has to grab Nefertina to get the diamond powder back. Nefertina ponders a life beyond the Mummies.
The un-bulked Mummies find themselves far from home. They have to struggle to make it back to their Sarcophagi in time to get recharged. Our recurring bickering cops, Joe and Bob, come close to nabbing them along the way. All four Mummies involved.