Early in the morning, the first rays of sunlight broke through the sky, faint and silvery like a fish's belly.
Gwen Tennyson woke up groggily, yawning as she carefully stepped around Ethen, who was still sleeping on the floor.
She went to the bathroom, washed up quickly, and tiptoed back.
"Mm…"
Ethen stirred, stretching and rubbing his eyes with his left hand.
"Sorry, Ethen—did I wake you?" Gwen asked softly, her voice full of guilt.
Ethen smiled, waving it off. "It's fine. I'm used to light sleep."
But then—
"Ah!!!"
Gwen's scream pierced the quiet morning. Her eyes widened in shock as she stared at Ethen's right arm—jet-black and monstrous, with a strange crimson device embedded into it. The watch's face looked like a demonic, scarlet eye.
"Ethen!" she gasped.
Grandpa Max frowned, studying the arm closely. "Is there anything unusual about your right arm?"
"Unusual?" Ethen looked at his hand and shrugged. "Not really. Except… it's a lot stronger."
He picked up a lemon, squeezed gently—and the juice burst out in a single motion, splashing perfectly into a glass of water.
He took a sip. "Freshly squeezed lemon juice."
"I want some too!" Ben Tennyson said eagerly. "Lemon juice made with a devil arm—awesome!"
"Are you sure this is safe?" Gwen asked, her tone full of concern. She could barely look at the eerie red watch on his arm.
Ethen smiled faintly and made another glass for her. "Don't worry. My arm's changed like this before. It usually goes back to normal by the next day."
The others exchanged worried glances.
"If it's not better tomorrow," Grandpa Max said firmly, "we'll have it checked."
After breakfast, Max went to wash up and then started the Rustbucket. Gwen and Ben stayed behind, curiously inspecting Ethen's strange arm.
First, Ben challenged him to an arm wrestle—then used Ethen's hand to crush soda cans into cool shapes. Gwen followed up with a magnifying glass, gently holding his hand and examining the details.
"Oh my gosh… this doesn't look like any Earth creature's arm," she murmured.
An hour later, the old Rustbucket drove down a misty forest road and stopped beside a wide, sparkling lake.
Max yawned. "You kids go have fun. I'll catch some sleep."
The lake's beauty was irresistible. Without hesitation, Ben, Gwen, and Ethen changed into swimsuits and headed for the water.
"Cannonball!" Ben shouted, leaping in and splashing everyone.
"Ah! It's freezing!" Gwen dipped her toes in, shivering. After a moment, she adjusted to the temperature and waded in fully.
Ethen crouched by the water, dipping his right arm in first.
The water around it… was warm?
He stepped in—and immediately felt the chill, except where his arm was. The devil arm was radiating heat.
"How weird… It's actually warm near you," Gwen said, swimming close and resting her hand against his arm. Her fear faded a little.
"Then let's swim together," Ethen said with a grin.
He started to move, his powerful arm slicing through the water easily. Gwen tried to keep up, but as they reached deeper waters, her pace slowed, and her nerves returned.
Ethen reached out and supported her shoulder gently. "Relax. I've got you."
Watching them from a distance, Ben frowned. "Hey! What are those two doing? They're supposed to be having a water fight, not a romance!"
He pouted and swam toward the center of the lake.
Suddenly—
Gurgle… gurgle…
Bubbles erupted violently around him.
"Huh? What's that?" Ben stopped, staring curiously at the disturbance.
BOOM!!!
A massive splash exploded upward, and Ben was flung back with a startled yell.
"Ben?!" Gwen cried.
Alarmed, Ethen instinctively pushed Gwen behind him and swam toward shore.
But before he could reach it—
Gurgle… gurgle…
The water in front of him boiled with bubbles again.
A cold dread crept over him.
"Gwen," he said quietly, "stay behind me. Don't move."
"O-Okay…" she whispered, rubbing her shoulder where he'd gripped her, and backed away.
BOOM!!!
A giant shadow burst from the lake, sending waves crashing. Rising nearly eight meters tall, it loomed in the mist—its massive frame like the legendary lake monster seen online.
"ROAR!"
The creature lunged straight at Ethen!
Too fast—no time to transform! Even the Omnitrix couldn't help now.
Ethen's eyes narrowed. He clenched his teeth and tightened his fist.
Muscles bulged, veins flared blue beneath his dark skin, and the air itself began to crackle around his arm.
The monster surged forward—
Ethen's fist blazed with a deep red glow.
He swung.
RUMBLE!!!
The impact thundered through the air. Waves exploded outward. The water monster froze mid-attack—then a massive bump swelled on its head.
With a dazed "Owww…," it retreated, diving back into the depths.
The lake fell silent again.
Ethen lowered his fist, breathing hard. His arm ached slightly—but he'd done it.
One punch had driven the monster away.
Just how strong would he be if he transformed…?
The Devil Watch truly was something else.
Then—
Gurgle gurgle!
"Gwen!" Ethen turned to see her struggling, coughing up water as she tried to stay afloat.
He didn't hesitate. He dove forward, wrapped an arm around her, and swam hard toward the shore.
"I'm fine," Gwen said between coughs, clinging to him tightly, her face flushed. "Really, I'm fine…"
Ethen smiled faintly as they reached the shore. Ben, soaked and exhausted, was already recovering.
The three of them hurried back to the Rustbucket.
"We've gotta tell Grandpa Max," Ben said, still panting. "There's a monster in that lake!"
Deep in the forest, hidden among the trees, a group of men watched with sinister smiles.
"Inform the boss about what we just saw."
"That kid's arm… It's not human. Looks like a devil's."
"He could be worth a fortune."
They exchanged malicious glances, then boarded small boats and headed toward the center of the lake.