This is book two in The Hollow series; books whose setting all take place in a village called Sleepy Hollow. Two siblings, Shane and Aimee, realize that their ancestor, Icabod Crane, has cursed Sleepy Hollow, and they feel a responsibility to check out any supernatural events that occur as a result of the gate or barrier being lowered due to their arrival in the village. A series of inexplicable drownings make the kids think that something unusual is occurring and they're correct. The water spirits or naiads are unhappy because someone is polluting the Hudson river and they want revenge. Book one was called Horsemen, but I read it quite a while ago and donated it to my school at the time so I don't have it in my current collection. Reading book one makes book two much easier to understand but it isn't vital; an intelligent reader can figure out what is going on without having read book one. ( )