Dementia 13 (1963)

While out on a rowboat with his wife Louise, John Haloran has a heart attack and dies. She casts his body overboard and hides his death, telling the family he left on an urgent business trip. Louise's main concern is that she can only hope to inherit part of his family fortune if he's still alive. The Halorans are a strange family.

They are still grieving over the death of the youngest daughter Kathleen, who drowned in a pond when she was very young. The family holds an annual ceremony of remembrance on the anniversary of her death. But this year someone is wielding an ax.. intent on murder.