The Rise & Fall of Darth Vader
"What is thy bidding, my Master?"
From light years away, on Coruscant, the Emperor replied, "There is a great disturbance in the Force."
"I have felt it," Vader said.
"We have a new enemy. The young Rebel who destroyed the Death Star. I have no doubt that this boy is the offspring of Anakin Skywalker."
Offspring?! The surviving tissue in Vader's throat suddenly went dry. Through his shock, he managed to say, "How is that possible?"
Without offering any explanation to support his stated conviction, the Emperor answered, "Search your feelings, Lord Vader. You will know it to be true. He could destroy us."
Having fought Luke Skywalker on Mimban, Vader was even more aware of the young man's powers than was the Emperor. But he also knew something else; Luke was as ignorant of their familial connection as Vader had been. If he had known the truth on Mimban, Vader thought, I would have sensed it. Still grappling with the Emperor's declaration, he struggled to find words that might discourage his Master's interest in Skywalker. "He is just a boy," Vader said. "Obi-Wan can no longer help him."
The Emperor believed otherwise. "The Force is strong with him," he said. "The son of Skywalker must not become a Jedi."
The Emperor had not said in so many words that he wanted Luke Skywalker dead, so Vader needing Skywalker alive to accomplish his goals took a different tack. "If he could be turned," Vader suggested, "he would become a powerful ally."
"Yes," the Emperor mused, as if he had not thought of that possibility. Vader could only imagine what the Emperor was thinking. The Sith had long maintained their rule of two: one Master, one apprentice. Even Vader knew that there wasn't room enough in the galaxy for three Sith Lords, and yet the Emperor's hooded eyes seemed to sparkle as he said more emphatically, "Yes. He would be a great asset. Can it be done?"
"He will join us or die, Master," Vader said. He bowed, and the Emperor's hologram faded out.
Now that the Emperor was interested in Luke Skywalker's fate, Vader knew he had to do everything in his power to find Luke before the Emperor found him.