Yoda was riding in a pack strapped to Luke’s back. Already sweating in his sleeveless tunic, Luke grabbed hold of a thick vine that stretched down from a high tree to the Dagobah swamp. He pulled himself up, hand over hand, carrying Yoda with him. Winged creatures flew through the humid air, but Luke ignored them.

At a designated branch, Luke turned, grabbed another vine, and swung away from the tree, down to the ground. He landed on solid soil, flipped his body forward over a broad root, and began to run through the swamp. As Luke raced in and out of the heavy ground fog, Yoda spoke to the back of Luke’s head, urging him on.

“Run!” Yoda said as he clung to Luke’s shoulders. “Yes. A Jedi’s strength flows from the Force. But beware of the dark side. Anger…fear…aggression. The dark side of the Force are they. Easily they flow, quick to join you in a fight. If once you start down the dark path, forever will it dominate your destiny, consume you it will, as it did Obi-Wan’s apprentice.”

Luke came to an abrupt stop and said, “Vader.” Breathing hard, he turned his head slightly to address Yoda and asked, “Is the dark side stronger?”

Yoda answered, “No…no…no. Quicker, easier, more seductive.”

“But how am I to know the good side from the bad?”

“You will know,” Yoda assured his new pupil, his voice a soothing rasp in Luke’s ear. “When you are calm, at peace. Passive. A Jedi uses the Force for knowledge and defense, never for attack.”

“But tell me why I can’t—”

“No, no, there is no why,” Yoda interrupted. “Nothing more will I teach you today. Clear your mind of questions. Mmm. Mmmmmmm.”

Luke closed his eyes to meditate.

R2-D2 beeped in the distance as Luke lowered Yoda to the ground. While the aged Jedi settled himself on a wide root, Luke stepped over to a tree branch, where he’d placed his shirt and weapon belt.

As Luke pulled on his shirt, he sensed something strange and deadly in the air. He turned to see a huge, dead, black tree, its trunk surrounded by a few feet of water. Giant, twisted roots formed a dark and sinister-looking cave on one side. Luke stared at the tree and a chill ran down his spine.

“There’s something not right here,” he said. “I feel cold, death.”

“That place…” Yoda said from his seat, “is strong with the dark side of the Force. A domain of evil it is. In you must go.”

Luke thought, He actually wants me to go in? But he also somehow knew the journey was necessary. It seemed the place was silently calling to him, beckoning. Hesitant, Luke asked, “What’s in there?”

Yoda said, “Only what you take with you.”

Luke looked warily between the tree and Yoda, then started to strap on his weapon belt.

Seeing this, Yoda said, “Your weapons…you will not need them.”

Luke gave the tree a long look, then shook his head and strapped on his belt. Yoda shrugged. As Luke walked away, the little droid trembled.

Luke brushed aside some hanging vines, then lowered himself into a hole. In the darkness, he could barely make out the passage that lay before him, but he proceeded deeper into it. There were roots, tangled and twisting up the walls, and the smell of rot and decay was everywhere. Could these roots bring life to the tree above? Somehow it seemed doubtful.

The space widened around him, and then he saw something move in front of him. There was a shadowy form, then mechanical breathing sounds, and a sense of dread.

Darth Vader.

The dark lord appeared from the blackness, and Luke took a few steps back. Time seemed to slow down, but Luke’s mind raced: How did Vader get to Dagobah? Is he looking for Master Yoda? Or is he here for…me? Then he remembered his lightsaber, and in an instant, the cave was illuminated by its blue blade.

Vader drew and activated his own red lightsaber, crossing his blade with Luke’s. Luke tried to concentrate but felt himself being distracted, drawn into the sound of labored breathing that came from Vader’s helmet. Then Vader attacked.

But Luke was ready. He angled his blade defensively to block Vader’s blade, and there was a loud, electric clash between the two lightsabers. The dark lord pulled back and swung again; Luke parried and prepared for Vader’s next assault. Their lightsabers again connected with a loud crackle of energy, until Luke broke free, swung hard—

—and cut off Vader’s head.

Sparks showered up from the neck of Vader’s decapitated form, his body toppled, and his helmet rolled across the cave floor.

Luke stared at the helmet, and its black oval lenses seemed to stare back. Then there was another shower of sparks, and the helmet’s faceplate burned away. The smoke cleared to reveal a face, cradled in the smoldering, broken shell of Vader’s helmet.

The face was Luke’s own.

This isn’t really happening, Luke thought as he stared at the head, into its cold, dead eyes. It’s all some kind of a hallucination or nightmare. But…what could it possibly mean?

While Luke made his way out of the cave, Yoda remained seated on the root. He looked at the ground and shook his head. Although Luke did not yet comprehend what had happened in the cave, Yoda knew that it had been a test. And that Luke had failed.