August 12, 2000, deep in the Barents Sea: a massive underwater explosion, then 135 seconds of agonizing silence, then a second blast so powerful it registers as a 4.2 magnitude earthquake across Europe. The Russian nuclear submarine Kursk, considered unsinkable, drops to the seafloor with 118 men aboard.

This episode unpacks the terrifying chain of events that destroyed a vessel built to take out entire US carrier groups. We examine the volatile chemistry that triggered the blasts, the systemic failures of a cash-starved navy, the 23 men who survived in the stern, and the political firestorm that engulfed Vladimir Putin. It matters as a profound lesson in the limits of technology when combined with human error, economic decay, and bureaucratic pride that refused outside help while lives ticked away.

• A faulty weld let high-test pe ...