Nobunaga had ordered several generals to lead their armies west to assist Toyotomi Hideyoshi who was fighting the powerful Mori clan. Mitsuhide was one of those generals. However, Mitsuhide defied Nobunaga's order and instead marched his army of 13,000 to Kyoto where Nobunaga was staying at the Buddhist temple Honnoji where he often stayed while visiting Kyoto. Nobunaga was killed by Mitsuhide's army at the temple called Honnoji and the assassination has since then been called the Honnoji incident. Mitsuhide's army then hunted down and killed Nobunaga's heir, his oldest son, Nobutada.
However, Mitsuhide would not have much time to consolidate his power. While other Nobunaga vassals hesitated and Tokugawa Ieyasu retreated to his domain for safety, Toyotomi Hideyoshi quickly and decisively marched his army from the west where he had been fighting the Mori clan. The two armies of Hideyoshi and Mitsuhide met at the Battle of Yamazaki where Hideyoshi crushed Mitsuhide's forces. Hideyoshi collected the head of Mitsuhide and presented it at the grave of Nobunaga.
In episode 17 of the NHK drama Tenchijin, the groundwork is laid for Nobunaga's assassination. At the end of the episode, Nobunaga is shown gravely insulting Mitsuhide in front of his other generals. Clearly the NHK drama is reinforcing the theory that Nobunaga insulted Mitsuhide.
What is very, very interesting is the last scene of episode 17 where Mitsuhide is having tea with Tokugawa Ieyasu following the incident with Nobunaga. Mitsuhide clearly implies that "something" should be done with Nobunaga. What is so interesting is that the drama makes it appear that Ieyasu knows exactly what Mitsuhide is referring to but he says nothing. In the several books I have read about this time period, including Japonius Tyrannus, there is no reference to Ieyasu meeting with Mitsuhide shortly before the assassination nor any evidence that Ieyasu knew anything about Mitsuhide's plans. Just an interesting observation about the show.