A deadly design flaw results in a horrifying rush hour bridge collapse that tragically leaves 13 dead in Minneapolis; using the latest science, experts investigate to reveal what went so catastrophically wrong on one of Minnesota's busiest crossings.

A devastating rail disaster outside the small town of Casselton, North Dakota, results in cargo erupting in massive explosions; experts use the latest science to investigate and uncover an engineering flaw poised for catastrophic failure.