Threshold

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 Interplaneta...