On Thule, an isolated mining colony, an unexpected native race - the Tersae - are encountered. Prompted by their Oracles who provide them weapons of advanced technology, the Tersae destroy Tyrus Ogden's mining camp but he survives aboard a Prescot 4800 surface excavator - the disarmed Bolo Mark XXIV DRK. The fate of a second camp rests upon the arrival of DRK and of his active service counterpart: Bolo Mark XXV KNN. One of them will pay the ultimate price for victory.