It's the year 2087, and on Jupiter's Moon Europa, under two miles of ice, fisheries catch massive shoals of a creature called Saarg, an extraterrestrial delicacy that's become standard fare on Earth's dinner tables. They're pretty expensive too, because besides tasting great, their meat is held to be a vaccine against cancer.

Jared Potts is a grungy long-haul space trucker from the Mars colony who is trying to cash in on the lucrative Saarg trade as an independent contractor for the monopolistic Allied EX Corp. And he really needs the break to pay off his debts. Otherwise he hasn't a prayer of regaining custody of the young son his ex-wife has spirited away to a place he despises-- Earth.

But Pott's troubles deepen after he pulls his beaten-up rig into the Mars inspection station and finds that all flights to Earth have been indefinitely suspended; and a quarantine imposed due to a strange dehydrating epidemic that's become rampant on the home planet. And he can't sell his cargo on Mars either, because, like himself, the colonists' dietary code forbids them from eating anything not grown on the "red planet".

Helped by Sarah "Jonesy" Jones, an inspector at the Mars station who is intent on seeing her ailing father, Potts decides to run the blockade. But when they arrive on Earth they soon discover that the wasting disease is really caused by consumption of the very fish that Potts has in his cargo hold. And worse, it's only the first stage in a process that can destroy all life on Earth.

Potts and Jonesy try to find the cure and save their loved ones, but time is running out, and the cards have been stacked against them by the greedy officials of the Allied EX Corp. But will it really be curtains for the human race, or is there still an unforeseen joker lurking in the unpredictable deck of evolution?