Seth is one of four foster children living with Mr. and Mrs. Rattles on the Yorkshire moors. In spite of the loving stability the Rattles provide, Seth runs away repeatedly. It has become a habit, he thinks, due to the horrendous beatings he had from his brutal stepfather. When a dark and menacing cloud appears over the moors, it is only Seth and the dog who realise there are alien beings in their home. But gradually all the children become aware of the fear exuded by these beings. It is Seth who must lead the aliens away from earth, back to their proper place. He hopes to come back, he tells the others, but he needs the time away to get over his vicious stepfather. Seth's fears are handled very well, and while the ending is not a happy one, it feels right. Good black and white illustrations and a powerful short book.