On April 20, 2010, an explosion tears through the Deepwater Horizon rig in the Gulf of Mexico, killing eleven workers and opening a leak a mile below the surface that nobody on the planet has ever had to stop before. This Horizon episode follows the 87-day scramble that followed, as BP engineers and government scientists try one fix after another: a containment dome that clogs with ice crystals, a 'top kill' that pumps heavy mud into the well and fails, and finally the relief wells drilled to intercept and seal the blowout for good. Interviews with the engineers who worked the crisis in real time lay out just how little was actually known about capping a leak at that depth and pressure, and how much of the response was improvised on the fly. Footage of the burning rig, the spreading slick, and the deep-sea robots sent down to fight it grounds the account in the physical scale of the problem. The film treats the spill as a technical siege as much as an environmental catastrophe.