Dementia 13 (1963)

Shocked by the sudden death of her spouse, young widow Louise Haloran--knowing that she will be excluded from the inheritance--hatches a daring plan to get her hands on her share. As a result, after carefully disposing of the body, the scheming woman pays a visit to her late husband's ancestral home in Ireland, the Castle Haloran, pretending that he is away on business. However, unbeknownst to Louise, a blood-thirsty ax-wielding murderer who lurks in the dark corners of the vast family estate has already set his sights on killing her at any cost. Indeed, there's an invisible killer in their midst. What mystery shrouds Lady Haloran's noble house?