They were sent to investigate the first extraterrestrial signal. What they found was beyond anything they could have imagined-or feared. On a voyage to a mysterious moon in the Alpha Centauri system, the UEA Centaurus meets with disaster. Only the quick thinking of the flight engineer, Rachel Terman, saves some of the crew. Crash-landing on the moon, trillions of kilometers from Earth, they struggle to carry out their mission and try to survive. But nothing has prepared them for what they will face. False readings on sensors. Bizarre nightmares. Crew members vanishing. Then Rachel discovers a blue, glassy lake. And everything changes. If the signal abides-will humankind fall?