A daring and resourceful paleontologist uncovers something at the infamous K-T boundary marking the end of dinosaurs in the fossil record -- something big, dangerous, and absolutely, categorically impossible. It's a find that will catapult her to the Martian moon Phobos, then down to the crater-pocked desert of the Red Planet itself. For this mild-mannered fossil hunter may just have become Earth's first practicing xenobiologist!