Terry, Helen, and Phil enter a cavern where they meet Rothgo, a wizard who needs help against Belor who has stolen a magical object called the Nidas. The children then enter the labyrinth of time and are hurled into the past.

The children arrive in neolithic Britain where they find Rothgo as a Druid Priest. Phil battles an evil dictator before Belor hurls the Nidas away in time.

The trio arrive in the caves beneath Nottingham where they battle the Sheriff of Nottingham and find Rothgo as a medieval magician. After defeating the Sheriff, Belor again hurls the Nidas away through time.

The children find themselves in the caves beneath the palace of the Grand Vizar in the far east. Rothgo helps the children rescue the Vizar before Belor discovers their plans and takes the Nidas away through time.

During the English Civil War, the children find Rothgo as a playwright while Belor is disguised as a housekeeper. After escaping a company of Roundheads, the children nearly find the Nidas before Belor hurls it through time again.

Arriving beneath Paris during the French revolution, Rothgo is under the spell of Belor who seeks to prevent him from helping the children. Finally reaching Rothgo, he is arrested to be executed just as Belor hurls the Nidas through time.

After briefly returning home, the children are sent by Rothgo to the original Labyrinth on the island of Crete. There the children must fight both a Minotaur and Belor to at last seize the Nidas.