On August 21, 1945, days after Japan's surrender, a 24-year-old physicist stood alone in a secret New Mexico laboratory holding a tungsten carbide brick over a plutonium core. Harry Daglian's slip of the hand made him the first known fatality of a criticality accident, and permanently changed how nuclear science is conducted.

This deep dive follows Daglian from a violin-playing kid in New London, Connecticut to MIT, Purdue, and the Manhattan Project. It explains the "tickling the dragon's tail" experiments, the instant of prompt criticality that bombarded his body with a fatal radiation dose, and the safety reforms written in his blood, including the eerie repeat accident that killed Louis Slotin with the very same core.

• Building a neutron reflector by hand to push the core toward criticality
• The dropped brick and the 5.1 ...