On a calm Sunday morning in 1978 residents of Bell Island, Newfoundland hear an odd, high-pitched hum, immediately followed by a sudden and terrifying blast resounding for hundreds of miles. Outbuildings are destroyed, livestock electrocuted, televisions explode and power lines vaporize. The Invisible Machine unravels the mystery of the Bell Island "boom" and in doing so takes a chilling look at the U.S. military's experimentation with electromagnetic pulse (EMP) weapons.