MS of Doctor Colin Mawson, biologist, and assistant (woman) in wooded area injecting radioactive solution to base of tree using syringe. MS of chart showing cross section of heavy water pile, PAN to CSs of doctors Lewis and Keyes discussing problem. MS of control panel, operator approaching, flipping switch and pushing buttons before walking off. CS of face of man at work. MS of worker moving pots of uranium oxide from floor into furnace opening in wall at Eldorado plant. CU of same worker wearing protecting mask to his face as he works. ESTABLISHING PAN of Fort Hope (uncertain information) on summer day, buildings visible among tree tops. MS of two men working in isotope room at Chalk River plant. CS of hand in rubber glove removing shield. ESTABLISHING SHOT of Chalk River buildings.