In the pitch black of March 1928, a curved concrete wall held back 12.4 billion gallons of water in a California canyon. The man who designed it was a self-taught engineering legend. What he did not realize was that the very mountain he had bolted his masterpiece to was dissolving like sugar, and within hours he would be responsible for one of the worst civil engineering disasters of the 20th century.

This episode examines the St. Francis Dam disaster as a profile of human hubris and unchecked authority. We follow William Mulholland's rise from ditch digger to the builder of the Los Angeles Aqueduct, the fatal geology of San Francisquito Canyon, the design changes made under pressure, and the forensic engineering that pieced together how the structure failed and killed at least 431 people.

• Mulholland rose from a ditch-clearing za ...