S1, E3: Something strange is happening in the Sierra Nevada skies. Over several decades, an estimated 2,000 aviation incidents have occurred there, with death tolls and disappearances far outnumbering those of the Bermuda Triangle. Why have so many pilots lost their lives or simply vanished without a trace? The phenomenon is explored on the ground and in the air, in hot deserts, cold mountains, high-tech labs, and even the outskirts of Area 51, all in search of the deadly truth of the Nevada Triangle.