First the cow goes dry and the horse acts spooked. An owl makes a shambles of the kitchen. Then a troll is seen nearby, and a huge bird sensed overhead. The family is on edge. Still, Mother must go off to Greenwillow to tend her daughter and new grandson, and Father must take her there--leaving teenaged Ansel and Rate alone on the farm for a few days. No sooner are the parents out of the way than a funny little man who calls himself Sinn Fein shows up with a case of mysterious instruments and offers to catch the troll. Gradually he reveals that the troll's surfacing and the bird's appearance signal an impending earthquake, and that he needs the troll's earbone for quake detection so he can alert the people in threatened areas. A wild storm does occur, but not an earthquake. When it's over, the man, the troll, and the bird have vanished; and the sensible vicar who shows up in its wake tells the boys that Sinn Fein is a common crackpot tramp, well known in another parish as ""the earthquake man."" It's a bit like the old stories where you wake up to find it all a dream; at the level of such tricks, Heath does a neat enough job of building up and blowing down successive beliefs and apprehensions.