In Tartarus, all the threads that weave through the Argosy Trilogy come together in a complex, tightly woven skein.

Captain Jacob Brinn, the genius who has challenged the whole world, departs on the voyage for which he'd originally designed the incredible Argo. This is both to decoy the enemy forces into pursuing him, as well as to rediscover humanity's past, and its fate.

Meanwhile, the crack team of Argonauts he left behind begin setting up a worldwide network of covert installations. Once completed, these will allow the Captain to hold the entire world hostage. But that is one thing the forces of order in the world will not allow.

An uncomprehending world watches in shock as the brutal final battle to the death begins.

And so, from the Earth to the surface of the Moon, the future of the human race is spelled out in hellfire itself.