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

My son has the Atreides sincerity , Jessica thought. He has that tremendous, almost naпve honor—and what a powerful force that truly is .
She saw that Paul's words had shaken Kynes.
"This is nonsense," Kynes said. "You're just a boy and—"
"I'm the Duke," Paul said. "I'm an Atreides. No Atreides has ever broken such a bond."
Kynes swallowed.
"When I say totally," Paul said, "I mean without reservation. I would give my life for you."
"Sire!" Kynes said, and the word was torn from him, but Jessica saw that he was not now speaking to a boy of fifteen, but to a man, to a superior. Now Kynes meant the word.
In this moment he'd give his life for Paul , she thought. How do the Atreides accomplish this thing so quickly, so easily?
"I know you mean this," Kynes said. "Yet the Harkon—"
The door behind Paul slammed open. He whirled to see reeling violence—shouting, the clash of steel, wax-image faces grimacing in the passage.
With his mother beside him, Paul leaped for the door, seeing Idaho blocking the passage, his blood-pitted eyes there visible through a shield blur, claw hands beyond him, arcs of steel chopping futilely at the shield. There was the orange fire-mouth of a stunner repelled by the shield. Idaho 's blades were through it all, flick-flicking, red dripping from them.
Then Kynes was beside Paul and they threw their weight against the door.
Paul had one last glimpse of Idaho standing against a swarm of Harkonnen uniforms—his jerking, controlled staggers, the black goat hair with a red blossom of death in it. Then the door was closed and there came a snick as Kynes threw the bolts.
"I appear to've decided," Kynes said.
"Someone detected your machinery before it was shut down," Paul said. He pulled his mother away from the door, met the despair in her eyes.
"I should've suspected trouble when the coffee failed to arrive," Kynes said.
"You've a bolt hole out of here," Paul said. "Shall we use it?"
Kynes took a deep breath, said: "This door should hold for at least twenty minutes against all but a lasgun."
"They'll not use a lasgun for fear we've shields on this side," Paul said.
"Those were Sardaukar in Harkonnen uniform," Jessica whispered.
They could hear pounding on the door now, rhythmic blows.
Kynes indicated the cabinets against the right-hand wall, said: "This way." He crossed to the first cabinet, opened a drawer, manipulated a handle within it. The entire wall of cabinets swung open to expose the black mouth of a tunnel. "This door also is plasteel," Kynes said.
"You were well prepared," Jessica said.
"We lived under the Harkonnens for eighty years," Kynes said. He herded them into the darkness, closed the door.
In the sudden blackness, Jessica saw a luminous arrow on the floor ahead of her.
Kynes' voice came from behind them: "We'll separate here. This wall is tougher. It'll stand for at least an hour. Follow the arrows like that one on the floor. They'll be extinguished by your passage. They lead through a maze to another exit where I've secreted a 'thopter. There's a storm across the desert tonight. Your only hope is to run for that storm, dive into the top of it, ride with it. My people have done this in stealing 'thopters. If you stay high in the storm you'll survive."
"What of you?" Paul asked.
"I'll try to escape another way. If I'm captured . . . well, I'm still Imperial Planetologist. I can say I was your captive."
Running like cowards , Paul thought. But how else can I live to avenge my father? He turned to face the door.
Jessica heard him move, said " Duncan 's dead, Paul. You saw the wound. You can do nothing for him."
"I'll take full payment for them all one day," Paul said.
"Not unless you hurry now," Kynes said.
Paul felt the man's hand on his shoulder.
"Where will we meet, Kynes?" Paul asked.
"I'll send Fremen searching for you. The storm's path is known. Hurry now, and the Great Mother give you speed and luck."
They heard him go, a scrambling in the blackness.
Jessica found Paul's hand, pulled him gently. "We must not get separated," she said.
"Yes."
He followed her across the first arrow, seeing it go black as they touched it. Another arrow beckoned ahead.
They crossed it, saw it extinguish itself, saw another arrow ahead.
They were running now.