Why do whales sing? What does the song mean?

Using artificial telepathy a Jesuit touch empath and an animal behavior specialist try to decode the cries of a captive dolphin; this leads them to a song sung by great whales which seems necessary to sea mammal survival.

The priest and the dolphin trainer, originally adversaries, begin to repair each other's brokenness as they realize the impact of the meaning of the song. What they uncover is heresy to religion and treason to the State.