It's 1972 and a new British Trident -- so named because of its three engines -- takes off from London, flies a few miles, and drops out of the sky, narrowly missing the town of Staines. Everyone aboard dies. In the absence of a cockpit voice recorder the investigators will have only the data from the flight recorder to work with. The only thing found wrong among the wreckage was that a handle that should have lowered the "droops" -- a kind of slat on the wing's leading edge -- showed that they were retracted. Interviews with other pilots revealed that the pilot, Captain Keys, was a by-the-book old-fashioned officer who felt that the growing demand for a strike among the other BAE pilots was presumptuous. He had had an outburst of bitter anger just before the flight.
The narrator calls Keys' mental state at take off "anxiety" caused by the argument, but the correct terms is "arousal." The captain was all het up. In psychology there is a thing called the Yerkes-Dodson law, according to which there is an optimal level of arousal for a given task, and the optimum level of arousal depends on the delicacy of the task. If you're trying to lift weights, you want high arousal. If you're performing surgery (or flying an airplane) you want a lower level of arousal. Not TOO low, otherwise you get careless and sloppy.
So was that the answer? Captain Keys was still highly PO'd and made a mistake? Not entirely. The handle for retracting the droops is next to the handle for retracting the flaps. And the responsibility for managing both handles isn't quite clear. The copilot can do it or the third pilot can help out by reaching forward and retracting the flaps. Since they feel much the same, and since the level of tension on the flight deck was high, it would have been easy to retract both the flaps and the droops prematurely, resulting in a stall.
Investigators also find that although he was asymptomatic the captain had sever clogging on his coronary arteries and may have suffered what they call a "heart attack" during take off, perhaps due to high blood pressure caused by the argument. They speculate that Keys was experiencing increasing pain and was nearly incapacitated. I'm dubious, because Keys evidently didn't say anything about it to the tower, but then he was the kind of man of honor who might NOT have complained.
There is also a kind of fail-safe mechanism. If the airplane is about to stall, the mechanism take over and points the nose down to gather speed and recover from the stall. It was working properly during take off but someone in the crew had disabled it.
Corrective measures were deployed. Eg., the handles for the flaps and the droops were remodeled so they were easily distinguishable by feel, and cockpit voice recorders were no required.