An innocent shopping jaunt for the Fifth Doctor and Peri ends in violence and incarceration as they become caught up in a mysterious transaction involving the sale of co-ordinates leading to Rovan's hoard — the ultimate treasure. The Doctor and Peri join the quest, but the Time Lord remains sceptical. What will they find — and why has it remained undiscovered for so long? The resourcefulness of the travellers is tested to the limits as they each race to be the first to the treasure. And among a seemingly endless array of tricks, tests and traps lurk some deadly surprises.