Contact: Astronomer Dr. Ellie Arroway receives an encrypted message, apparently from a solar system many light-years away.

Sphere: Far below the surface in the mid-Pacific, U.S. officials have isolated what may be the greatest discovery in human history. They've found a huge spacecraft that plunged into the depths--300 years ago. What is the spacecraft's origin? After three centuries, could there still be a living intelligence aboard?