The conspiracy of evil - Christian Jacq

Despite the pharaoh Sesostris's determation, despite the combined efforts of his generals who are searching, in vain, for the culprit, despite daily prayers and the devoted care of the queen and the seven priestesses of the goddess Hathor, the beautiful acacia tree of Abydos is dying.
But the most mysterious of the priestesses, the one who haunts the nights of young Iker the scribe, has an idea: to save the 'Tree of Life', a new pyramid must be built at Dachur, dedicated to Osiris. Sesostris agrees, and plans are afoot to begin building.
But what Sesostris doesn't know is that a triple conspiracy has been hatched against him. On the one hand, the Herald, the bearded devil who preaches to the desert tribes, has decided to seize power by having the pharaoh murdered. On the other, at the king's court, an ambitious, thieving traitor has only one solution: to get rid of his master. Finally Iker himself, deceived by appearances, believes that the moment has come to settle his scores. The conspirators only have to await their opportunity ...