Emperor Domitian (51-96 CE) used to say that the prynceps are unhappy because they do not believe reports of the plot until they are murdered.
These words were probably not uttered without reason. Domitian at the end of his reign became very suspicious. He was almost always accompanied by a watch. He placed many mirrors in his palace so that he could see what was happening behind his back. His suspicions were correct. Senators were not favourable to him, and neither were many of his associates.
Finally, his wife Domitia entered into a conspiracy with his trusted liberators and two Praetorian Prefects. He was stabbed to death in his palace on September 18, 96 CE. Thus ended the reign of the Flavian Dynasty.