The Eye of Ra, Episode Four

The Eye of Ra, a diamond reputed to have the power to turn people into chalk, is high on eccentric chessmaster Ceribraun's shopping list. Believing that the diamond has turned Mr. Sweet into a chalk statuette, Tarot decides to act. He soon finds himself a prisoner of Ceribraun's talking computer, and in danger of being crushed to death between gigantic robotic chess pieces.