 Dr. Kharmusi, a criminal scientist, has developed a "thermal prism," which generates intense heat beams. UNCLE recruits Luther Sebastian, wanted for various crimes in 22 countries, because he designed the kind of safe where Kharmusi keeps the prism. Napoleon Solo infiltrates Kharmusi s base of operations as an amoral businessman while Illya Kuryakin and Sebastian work to steal the device. However, Annie, whose boyfriend was framed for murder by Sebastian, complicates matters.