Dodecahedron is the third book in the Ocellus Series, for age 14+ and is set millions of years before the events recorded in Ocellus: The Story of the Twelfth Stone.

Following the religion wars five thousand years ago, society survives in giant protective domes.

Seventeen-year-old Tanun rebels against the repressive society that has evolved and is banished to the outside. He follows an ancient railway track into a tunnel and discovers a glassy-black oval stone amongst the rocks and rotting sleepers. The stone is so unusual he keeps it, and after emerging from the tunnel sees on one face an engraving of a dodecahedron.

Soon, a friendly alien, Cassièl, confronts him and says he has searched for the dodecahedron stone for trillions of years. He warns Tanun he is in great peril from the evil KimMorii, who stole the stone, because if they found him and took the stone, he would die. Meanwhile, Tanun's younger brother, Chyke, has escaped and caught up with him.

Cassièl leads the boys to another, more liberal dome where they both develop a close relationship with Joor-Jen, a fierce young woman who trains them in close combat and helps them adapt to their new life.

The KimMorii invade and civil war erupts. In the chaos of war, Tanun has to deal with double-agents, the kidnap of his brother, and deceit and betrayal, while keeping Dodecahedron safe until Cassièl can successfully and safely retrieve it.

Like the Ocellus and Mobius stories, Dodecahedron is huge in scope and deep in emotion and takes the reader into alternative universes, repressive societies, and fateful relationships.