Across Australia's industrial sites, machines that never stop running eventually break, and this episode follows the specialists called in to fix them under pressure. At Hangar 3, licensed aircraft maintenance engineer Steven works through a multimillion-dollar repair job where one mistake could bring six tonnes of jet engine crashing down. Elsewhere, fitter and turner Paul tackles worn bearings on the arm of a 550-tonne excavator, a job that demands over 24 hours of setup for a repair window of just 30 seconds. Cameras follow these crews on site, deep underground and high off the ground, capturing the actual mechanical work in close detail rather than reenacting it: measuring tolerances, rigging heavy parts, and racing deadlines in harsh conditions. The episode moves between these two main jobs, letting the tradespeople explain the stakes and the physics of what they're doing as they do it. It is a straightforward look at the trades keeping heavy industry running when the biggest machines fail.