After a severe tropical storm damages an underwater research station, Mirai and her crew are asked to help repair the damage and lend aid to the creatures in the surrounding biosphere. What they uncover there is more dangerous than they could have realized and will take all their skills, and help from an unexpected ally, to make right.

After a severe tropical storm damages an underwater research station, Mirai and her crew are asked to help repair the damage and lend aid to the creatures in the surrounding biosphere. What they uncover there is more dangerous than they could have realized and will take all their skills, and help from an unexpected ally, to make right.