Luke sat in the dark, hidden from Vader's eye by a large console.
All was quiet but for the low hum of the Sith lord's lightsaber.
"You cannot hide forever, Luke."
"I will not fight you." The decisiveness in his voice was strong. Luke listened intently for Darth Vader's footsteps, his eyes tight shut.
"...Give yourself to the Dark side. It is the only way you can save your friends. Yes," Vader said, matter of factly. "Your thoughts betray you. Your feelings for them are strong. Especially for..." And there it was. Luke's mastery of the Force was not enough to hide his most powerful feelings and most important thoughts. The more he tried to hide them, the more obvious they became. "...Sister. So, you have a twin sister. Your feelings have now betrayed her too. Obi-Wan was wise to hide her from me... Now his failure is complete." Vader was close now. Very close. "If you will not turn to the Dark side," Vader said, thoughtfully, "then perhaps she will."
The hiss of Luke's saber igniting was drowned out by his furious voice. "NEVER!" Vader turned around just in time. Luke's lightsaber was thrust at him, a glowing green blur, and he parried with his own. His strength was startling. With his fury no longer in check, Luke Skywalker's attacks became brutal, wild. He swung wildly, hitting a console. Vader ducked out of the way, bringing his weapon to bear. The tubes of light crashed and tangled again with a clap. He backed away, and Luke advanced with reckless abandon. No longer thinking of defense, each movement Luke's weapon made was one of hateful aggression. As they dueled, passing the stairs leading to Palpatine's throne, Luke fought harder, his swings becoming more pronounced. It took everything Vader had to stave off his attacks. He blocked an overhead strike, then moved again and fell against the railing of the walkway they were on. Luke bashed repeatedly against the Sith's lightsaber, finally knocking it out of the way and severing his hand .
"Aahhh!" Vader let out a surprised cry as his stump of an arm sparked. He fell back, supporting himself with his remaining hand, and a malicious cackle came from behind the two fighters.
"Goooood..." Palpatine's voice had a callous tone to it. "Your hate has made you powerful. Now, fulfill your destiny... and take your father's place at my side!" These words seemed to bring back some sense to Luke. He looked down at the defeated former Jedi, who still held his arm out in feeble defense, then down to his own mechanical hand, which had replaced the one he lost on Bespin. He calmed himself, as Yoda had taught him, and deactivated his weapon.
"Never," Luke said, turning to Emperor Palpatine. He tossed away his lightsaber. "I'll never turn to the Dark side." Palpatine's grin vanished. "You've failed, your highness," Luke said defiantly. "I am a Jedi, like my father before me." Now Palpatine wore a very ugly look. "So be it... Jedi."