From "Manual of Muad'Dib" by the Princess Irulan

I must be bold now , he thought.
"You taught me that my own hands must remain clean," he said.
"Ah, yes," the Baron said. "When you face the Emperor, you must be able to say truthfully that you did not do the deed. The witch at the Emperor's elbow will hear your words and know their truth or falsehood. Yes. I warned you about that."
"Why haven't you ever bought a Bene Gesserit, Uncle?" Feyd-Rautha asked. "With a Truthsayer at your side—"
"You know my tastes!" the Baron snapped.
Feyd-Rautha studied his uncle, said: "Still, one would be valuable for—"
"I trust them not!" the Baron snarled. "And stop trying to change the subject!"
Feyd-Rautha spoke mildly; "As you wish, Uncle."
"I remember a time in the arena several years ago," the Baron said. "It seemed there that day a slave had been set to kill you. Is that truly how it was?"
"It's been so long ago, Uncle. After all, I—"
"No evasions, please," the Baron said, and the tightness of his voice exposed the rein on his anger.
Feyd-Rautha looked at his uncle, thinking: He knows, else he wouldn't ask .
"It was a sham, Uncle. I arranged it to discredit your slavemaster."
"Very clever," the Baron said. "Brave, too. That slave-gladiator almost took you, didn't he?"
"Yes."
"If you had finesse and subtlety to match such courage, you'd be truly formidable." The Baron shook his head from side to side. And as he had done many times since that terrible day on Arrakis, he found himself regretting the loss of Piter, the Mentat. There'd been a man of delicate, devilish subtlety. It hadn't saved him, though. Again, the Baron shook his head. Fate was sometimes inscrutable.
Feyd-Rautha glanced around the bedchamber, studying the signs of the struggle, wondering how his uncle had overcome the slave they'd prepared so carefully.
"How did I best him?" the Baron asked. "Ah-h-h, now, Feyd—let me keep some weapons to preserve me in my old age. It's better we use this time to strike a bargain."
Feyd-Rautha stared at him. A bargain! He means to keep me as his heir for certain, then. Else why bargain. One bargains with equals or near equals!
"What bargain, Uncle?" And Feyd-Rautha felt proud that his voice remained calm and reasonable, betraying none of the elation that filled him.
The Baron, too, noted the control. He nodded. "You're good material, Feyd. I don't waste good material. You persist, however, in refusing to learn my true value to you. You are obstinate. You do not see why I should be preserved as someone of the utmost value to you. This . . . " He gestured at the evidence of the struggle in the bedchamber. "This was foolishness. I do not reward foolishness."
Get to the point, you old fool! Feyd-Rautha thought.
"You think of me as an old fool," the Baron said. "I must dissuade you of that."
"You speak of a bargain."
"Ah, the impatience of youth," the Baron said. "Well, this is the substance of it, then: You will cease these foolish attempts on my life. And I, when you are ready for it, will step aside in your favor. I will retire to an advisory position, leaving you in the seat of power."
"Retire, Uncle?"
"You still think me the fool," the Baron said, "and this but confirms it, eh? You think I'm begging you! Step cautiously, Feyd. This old fool saw through the shielded needle you'd planted in that slave boy's thigh. Right where I'd put my hand on it, eh? The smallest pressure and—snick! A poison needle in the old fool's palm! Ah-h-h, Feyd . . . "
The Baron shook his head, thinking: It would've worked, too, if Hawat hadn't warned me. Well, let the lad believe I saw the plot on my own. In a way, I did. I was the one who saved Hawat from the wreckage of Arrakis. And this lad needs greater respect for my prowess .
Feyd-Rautha remained silent, struggling, with himself. Is he being truthful? Does he really mean to retire? Why not? I'm sure to succeed him one day if I move carefully. He can't live forever. Perhaps it was foolish to try hurrying the process.
"You speak of a bargain," Feyd-Rautha said. "What pledge do we give to bind it?"
"How can we trust each other, eh?" the Baron asked. "Well, Feyd, as for you: I'm setting Thufir Hawat to watch over you. I trust Hawat's Mentat capabilities in this. Do you understand me? And as for me, you'll have to take me on faith. But I can't live forever, can I, Feyd? And perhaps you should begin to suspect now that there're things I know which you should know."
"I give you my pledge and what do you give me?" Feyd-Rautha asked.
"I let you go on living," the Baron said.
Again, Feyd-Rautha studied his uncle. He sets Hawat over me! What would he say if I told him Hawat planned the trick with the gladiator that cost him his slavemaster? He'd likely say I was lying in the attempt to discredit Hawat. No, the good Thufir is a Mentat and has anticipated this moment .
"Well, what do you say?" the Baron asked.
"What can I say? I accept, of course."
And Feyd-Rautha thought: Hawat! He plays both ends against the middle . . . is that it? Has he moved to my uncle's camp because I didn't counsel with him over the slave boy attempt?
"You haven't said anything about my setting Hawat to watch you," the Baron said.
Feyd-Rautha betrayed anger by a flaring of nostrils. The name of Hawat had been a danger signal in the Harkonnen family for so many years . . . and now it had a new meaning: still dangerous.
"Hawat's a dangerous toy," Feyd-Rautha said.
"Toy! Don't be stupid. I know what I have in Hawat and how to control it. Hawat has deep emotions, Feyd. The man without emotions is the one to fear. But deep emotions . . . ah, now, those can be bent to your needs."
"Uncle, I don't understand you."
"Yes, that's plain enough."
Only a flicker of eyelids betrayed the passage of resentment through Feyd-Rautha.
"And you do not understand Hawat," the Baron said.