The second book in the popular Boundary SF adventure series co-authored by multiple New York Times bestseller Eric Flint and Ryk E. Spoor.

When the strange fossil she'd discovered gave her a trip to Mars, Helen Sutter thought she'd gone about as far as any paleontologist would ever go in her lifetime. But when you’re married to an overconfident super-sensor expert for the only private agency in space – the Ares Corporation – and your best friend is a former secret agent for the Interplanetary Research Institute of the United Nations, there's always somewhere farther to go.

Soon Helen’s new discoveries will lead her to the mysterious asteroid Ceres and beyond in a desperate race to reach Jupiter's perilous miniature system of radiation-bombarded moons. It seems the next gold rush is on–for alien technology.

And there are people willing to do anything to get it – even if they must start the Solar System’s first interplanetary war!

Praise for the Boundary series:
“A genial, fast-paced sci-fi espionage thriller [that is] light in tone and hard on science…” –Publishers Weekly on Threshold