When Billy and Kane are talking by the pond, Billy mentions that they always hold black umbrellas,but at the funeral Lady Haloran and Billy are holding black umbrellas, but Richard is holding a white umbrella.
In the movie's latter half Dr. Caleb enters a work shed and discovers the body of Louise and the lifelike Kathleen doll. Carefully picking up the doll, he closes the shed door, and immediately in the next scene is shown walking with the doll in his arms and a cigar in his mouth.
When Billy is holding the candle while talking about being stressed, the candle has been smoldering quite a bit of smoke and the next shot shows the candle is lying on the table and there is absolutely no smoke.
The goof item below may give away important plot points.
When Louise strips before she jumps into the pond, she has on white underpants, then when swimming she has on black underwear. After she gets axed at the edge of the pond and dragged away, she again has on white.