Die, Monster, Die! (1965)

Nahum Witley (Boris Karloff) explains, after he buries his wife (who became a monster because of the "radiation"), that the "radioactive" stones he used on the plants in the greenhouse come from a larger stone (a meteorite) that fell from the sky. Nahum considered it a gift from Heaven and decided to use the stone to turn the land around the mansion into lush, fertile land in order to associate the Witley name with something good (because one of his ancestors did horrible things in the past and the town fears and hates the Witleys). The radiation from the stones affected his wife, Helga and Merwyn when they entered the greenhouse. Stephen tells Mr. Witley to get rid of the larger stone because it's too dangerous. Witley goes to the room where the stone is kept, and as he's about to smash the stone with an axe, suddenly Helga attacks him. She falls, gets in direct contact with the stone and dies. Mr. Witley is affected by the radiation and attacks Stephen and Susan. Susan moves out of the away as her father lunges and he falls down to the first floor of the house and dies. His radioactivity causes the house to burn down and Susan and Stephen run away. Stephen tells Susan that Mr. Witley's death wasn't caused by a family curse but his own ambition and that he had the choice of using the stones as a benefit to the world...

Racer X