The astronomer Nasir-ed-deen was not the only involuntary captive of Alamoot. Ala-ed-deen sent once to Farsistan to the atabeg Mozaffer-ed-deen, to request that he would send him an able physician. Requests from Alamoot were not lightly to be disregarded, and the atabeg despatched the imam Beha-ed-deen, one of the most renowned physicians of the time, to the mountains of Jebal. The skill of the imam proved of great benefit to the prince, but when the physician applied for leave to return to his family he found that he was destined to pass the remainder of his days in Alamoot, unless he should outlive his patient. The imam's release, however, was more speedy than he expected. Ala-ed-deen, who had several children, had nominated the eldest of them, Rukn-ed-deen (_Support of Religion_), while he was yet a child, to be his successor. As Rukn-ed-deen grew up the people began to hold him in equal respect with his father, and to consider his commands as equally binding on them. Ala-ed-deen took offence, and declared that he would give the succession to another of his children; but, as this directly contravened one of the Ismaïlite maxims, namely, that the first nomination was always the true one, it was little heeded. Rukn-ed-deen, in apprehension for his life, which his father threatened, retired to a strong castle to wait there the time when he should be called to the succession. Meantime the tyranny and caprice of Ala-ed-deen had given many of the principal persons about him cause to be apprehensive for their lives, and they resolved to anticipate him. There was a man at Alamoot named Hassan, a native of Mazenderan, who, though no Ismaïlite, was of a vile and profligate character. He was the object of the doating attachment of Ala-ed-deen, and consequently had free and constant access to him. Him they fixed upon as their agent, and they found no difficulty in gaining him. Ala-ed-deen, whose fondness for breeding and tending sheep had never diminished, had built for himself a wooden house close by his sheep-cotes, whither he was wont to retire, and where he indulged himself in all the excesses in which he delighted. Hassan of Mazenderan seized the moment when Ala-ed-deen was lying drunk in this house, and shot him through the neck with an arrow. Rukn-ed-deen, who is said to have been engaged in the conspiracy, assuming the part of the avenger of blood, the murderer and all his family were put to death, and their bodies committed to the flames; but this act of seeming justice did not free Rukn-ed-deen from suspicion, and the bitter reproaches of his mother were poured forth on him as a parricide. The termination of the power of the Ismaïlites was now at hand. Rukn-ed-deen had hardly ascended the throne of his murdered father when he learned that an enemy was approaching against whom all attempts at resistance would be vain. Chapter XI.