As Hurricane Helene dumped record levels of rain on East Tennessee, the swollen Nolichucky River overtook a small plastics factory and the only road out. A panicked group of workers, who had climbed aboard a truck’s trailer in front of the plant, were swept away by the raging floodwater.

An NBC News investigation and timeline reveals how events quickly and dramatically unfolded amid a "one-in-5,000-year flood."