A series of construction errors causes a devastating flood that brings Chicago to a standstill. A deadly accident traps hundreds in a smoke-filled Alpine tunnel, with no ventilation. Three boilers explode on a Mississippi riverboat resulting in thousands of deaths and earning the disaster the title of the worst in maritime history. Two buildings, halfway around the world from each other, collapse from the same type of shoddy construction methods--14 years apart. And a cockpit warning system malfunctions, causing a fiery, fatal crash before the jetliner ever takes off. We interview design and construction experts as we investigate what went wrong. And we talk with rescue personnel, eyewitnesses, and victims as we visit the tragedies' sites to see what improvements have been implemented to insure against these kinds of disasters.