Tory Brennan, the great-niece of Dr Tempe Brennan, and the Virals return for a third thrilling adventure on Loggerhead Island.

The Virals are put to the ultimate test when they find a geocache containing an ornate puzzle box.

Shelton decodes the cipher inside, only to find more tantalising clues left by 'The Gamemaster'.

A second, greater geocache is within reach...if the Virals are up to the challenge.

But the hunt takes a dark turn when Tory locates the other box, a fake bomb, along with a sinister proposal from The Gamemaster.