A Swiftly Tilting Planet (Time Quintet #3)
The Murry and OKeefe families enlist the help of the unicorn, Gaudior, to save the world from imminent nuclear war. They are not alone in their quest. Charles Wallace's sister, Meg -- grown and expecting her first child, but still able to enter her brother's thoughts and emotions by "kything" -- goes with him in spirit. But in overcoming the challenges, Charles Wallace must face the ultimate test of his faith and will, as he is sent within four people from another time, there to search for a way to avert the tragedy threatening them all. - Publisher.