Hundreds of years in the future, mankind and dolphins live peacefully together and share the earth. Dolphins, who are much more intelligent than they seem, act as the earth's caretakers, while dolphins and humans explore the galaxy. An alien force, known as the Foe, seeks to end this happy existence. The Foe damages the Earth's defense system, and alters history for the worse. One extraordinary dolphin, Ecco, must travel through time to set things right.