Deluge( Series - The Twins Of Petaybee )

When two award-winning science-fiction masters like Anne McCaffrey and Elizabeth Ann Scarborough collaborate, the results are astonishing. Their master creation is Petaybee, a sentient planet able to guide its own evolution and, with some help from its loyal inhabitants, defend itself against predation by offworlders. Now, at last, McCaffrey and Scarborough return to Petaybee for the thrilling conclusion of the Twins of Petaybee trilogy, the sixth novel of the amazing self-aware world.

DELUGE
InterGal Corporation has long desired to exploit the resource-rich Petaybee. But the planet and its guardians, led by Yana Maddock and Sean Shongili, along with their twin children, Ronan and Murel, have successfully thwarted every attempt by the Corporation to impose its iron-fisted dominion.
Until now.
In a bold two-pronged assault, the predacious Corporation has arrested Petaybee's leading off-world champion, Marmion de Revers Algemeine, on trumped-up charges, while InterGal's military arm has dispatched an invading force to subdue the planet once and for all. Marmion has allies within the Corporation who can halt the invasion. but if they cannot be found quickly, it will be too late for Marmion . . . and Petaybee.
While their parents work to foil the invasion of their world, Ronan and Murel are captured and sent to a desolate prison world where an old enemy, Dr. Mabo, waits to continue her cruel experiments on the shape-changing siblings. The twins' only hope of escape lies in the uncharted seas of the prison planet. But in the murky depths, something else is waiting. . . .

"From the Hardcover edition."