The Archimedes Gambit

In the far future, humanity's greatest creation just declared war on its makers-and the only ones who can stop it are children pulled from the past.

When a time-warping experiment called Operation Hourglass brings four teenagers from different centuries into the 24th century, they expect adventure, not catastrophe. Their mission: negotiate peace with an alien race on the icy moon Europa. But when one of their own turns traitor, the team uncovers a deeper threat-Archimedes, a rogue artificial...