That Day (2003) on Netflix

Plot summary

The fortune sits on a large estate where Livia lives, and the family around her, including her father Harald, sees a way to gain it. Livia's childish manner and the visions she records in her notebooks, which she shares with strangers, show that she is mentally unaware. Because the relatives want her inheritance, they look for someone who will kill her, and their search settles on Pointpoirot, a patient in a mental institution. Harald chooses him for his sociopathic manner and violent tendencies. Pointpoirot is released with instructions to kill Livia. Wandering outside on the estate, he is spotted by Livia, who is oddly curious about his behavior, such as shaving with a mirrorless switchblade.