1x03 Dead in the Water

Taking a break from the search for their father, Sam and Dean head to Lake Manitoc in Wisconsin for a possible case. Three drownings have occurred there within a year, with the dead bodies mysteriously disappearing in the lake. The brothers soon come to believe that the spirit of a young boy haunts the lake, and learn that the local sheriff (Daniel Hugh Kelly) and the father of the latest victim accidentally caused his death when they were children. Out for revenge, the spirit targets the sheriff's daughter Andrea (Amy Acker) and mute grandson Lucas (Nico McEown). It eventually pulls Lucas into the lake, so the sheriff gives himself over to the spirit, saving his grandson.