Eye of the Cat (1969) on Netflix

Plot summary

Danielle, called Aunt Danny, is a wealthy elderly woman who lost two-thirds of her lungs and spends her nights in an oxygen tent. She gets around in a wheelchair and keeps dozens of cats in her mansion. Her nephew Luke looks after her, though she has no fondness for him. Her other nephew, Wylie, has an intense fear of cats, because one attacked him when he was a child. Kassia Lancaster, the beauty parlor attendant who tends Danny, watched her collapse there and fetched Wylie; she proposes shutting off the oxygen supply to Danny's tent to kill her, and he agrees.