Three children stumble upon imprisoned sorcerer Rothgo and are drawn into a mysterious search through time for the magical Nidus, which has been stolen by the evil witch Belor.
Belor returns again and Phil is lured into Delta Time – an alternative history where fiction exists – by the unreliable magician Lazlo. Lazlo and Phil are soon dying of a disease, and the only hope rests in finding the scarabs.
Lazlo, as the incompetent chemist Dr Jekyll, plans to transform himself into the infamous Mr Hyde. Meanwhile, Belor—as Mrs Hyde—takes control of Victorian London's criminal underworld.
Phil flies through time to find Lazlo as a seedy priest at the time of the Incas. They encounter Belor in the guise of an evil native princess in league with the Spanish Conquistadors.
Lazlo, as Thomas Farriner, has a mob on his heels when his baker's shop begins the Great Fire of London. Belor appears as a countess with magical powers known to the Lord Mayor himself.
Phil and Lazlo, now a ratcatcher, search the catacombs beneath the Paris Opera. Belor poses as a young girl abducted by the fabled Phantom of the Opera and finds the scarab hidden in an unlikely place.
Phil arrives at the court of Kubla Khan in ancient China. Lazlo, as Marco Polo, struggles to regain the scarab, but is denied possession by a rebellion led by Khan's son, Aybars, with some aid from Belor.
Phil arrives in ancient Britain to find Lazlo in the guise of Merlin, the only one who knows the secret of Excalibur in the days when King Arthur's power is waning in the face of Belor's evil as Morgan Le Fay.