Naïda

The glowing structure at the bottom of a lonely northern lake is not of this Earth. But Michael Hart can't stay away.
When a childlike symbiotic alien being makes its home in Michael's body, his actions will shape the future of humankind. Tricked by an alien artificial intelligence into sending a signal that will bring interstellar explorers back to Earth, he fears the worst and embarks on a journey to prevent an invasion, but the maturing symbiote may have a different agenda. Michael develops extraordinary new abilities that neither can fully predict. Will the changes make him superhuman, or the puppet of alien masters? A hero? Or the greatest traitor that ever lived?
Because he is no longer alone, not even in his own body. There is another.
Naïda.