When Yanaba Maddock came to the planet of Petaybee, she was a washed out member of InterGal, her lungs almost non-functional because of a gas attack. In coming to the Planet, she was introduced to Petaybee itself, a living planet, cured of her lung problems, and fell in love with Sean Shongili, a human genetically engineered to be a Selkie, a man who turns into a seal when he becomes immersed in water.
Yana and Sean fell in love and conspired with the planet to get Intergal off the planet, which did not want to be terraformed. The people of the planet, mostly native Americans with some Irish, succeeded, But in the process, they learned that the natives of Petaybee, as adults, are so well adapted to the planet, that to leave it is to die. They can leave as children, or young adults, but as adults, they are bound to the planet.
Sean and Yana married and had two children, Murel and Ronan, twins and inheritors of Sean's selkie genes. Currently, they are ten years old. But InterGal isn't finished with Petaybee yet, and they still want to exploit the planet for its mineral wealth, buried deep in the planet. Doing this, however, means getting the Petaybeans, not to mention Yana, Sean and their children, out of the way.
Recently, Murel and Ronan discovered a race of "Deep Otters" who were actually shapeshifting aliens. Ronan and Murel befriended them, along with a River Otter friend of theirs, Sky. The Aliens agreed to take Murel and Ronan to their friend Marmie, better known as Marmion de Revers Algemeine, before she can be arrested on trumped-up charges. And a group of InterGal employees is coming to Petaybee to arrest the inhabitants and take them to what is essentially a prison planet, although they call it a "reintegration camp".
Warned by the others, the Petaybeans take shelter in the underground caves. The planet helps them by enveloping the main village, Kilcoole, in a massive blizzard. Yana and several other Petaybeans attempt to sneak back aboard the ship disguised as soldiers, and hijack the ship to search for other settlers already captured.
Ronan and Murel are barely in time to warn Marmie's people at the space station she owns, but Marmie has already been taken in her own personal spaceship, along with her crew. Eventually they and Sky are captured and are taken to a prison world, Gwinnet Incarceration Colony. Not only are they on the colony, but so is Dr. Mabo, a rogue geneticist who wants to experiment on the twins to find the source of their powers. Not only will they have to evade Dr. Mabo, but escape and find Marmie before the people at the Prison can torture her and possibly kill her.
But Marmie is no stranger to Prison, or to the Gwinnet Incarceration Colony. Indeed, she was imprisoned here as a child, and was raised for years in the cells. Her parents had been imprisoned for being on the wrong end of a political rebellion, and Marmie, their daughter, had been taken away from them when the Commandant's wife wanted a girl-child of her own to raise. Now Marmie is back. But she has friends on her side, and her very intelligent cat, Zuzu, who has found Sky, and they are waging their own war on the Prison complex.
InterGal has nearly tied the Petaybeans in knots. Can they undo the knots and keep themselves and their planet free from the machinations of InterGal?
This series follows up Anne McCaffrey's original Petaybee books and is officially named "The Twins of Petaybee". Most of the action with the twins occurs offworld, both at the space station and on Gwinnet. Occasionally, the twins are scarily advanced for ten-year olds, such as thinking about people of the opposite sex being attracted to them, or likewise, in being attracted to others that way. Now, I know the twins are unusually intelligent, but even then... I think many ten-year old boys are still thinking of girls as "icky" at this stage, not thinking of liking or being attracted to them. Neither are girls at that age, usually. In fact, despite the story describing them as being "not quite eleven", I got the image that these two were nearer to being fifteen or so in the way they were described, mentally and emotionally, at least. Even the cover picture of Deluge is of a female, presumably Murel, who looks far, far older than ten (or "not quite eleven"). And adult, albeit an adult with a small chest, but still an adult.
Aside from that, the story is very well done and plotted, though some things are not elaborated on and left as puzzles right up until the very end. And one of the twins nemeses is killed at the end of the story, which leads me to believe the story of the twins will probably be ended in the next book. So, aside from the issues of the twins acting in some ways more mature than the age they are stated to be, this is an exciting book that adds very well to the Petaybee series.