Spindrift (Coyote Series #4)

The EASS Galileo disappeared decades ago while investigating an unidentified object, code-named Spindrift. Now the Galileo's shuttle has returned carrying three surviving expedition members, who still appear to be the same age they were when they departed. They report that they have, indeed, made contact with an extraterrestrial race-and become enmeshed in a conflict that brought them face to face with the most apocalyptic force in the galaxy.