So, did eating those berries affect Tuffnut? And who is this masked rider? All will be revealed very soon...

He was putting the first log down in their fire pit when he first felt it; a sort of fatigue, numbing but faint. They had dug a deep trench right at the very peak of the hill and were preparing to set a great beacon inside, hoping at least the smoke column would be visible from Berk. However, as he moved more and more logs, Tuffnut began to feel more and more weak. His arms began to shake, as did his legs, and his skin took on a deathly white pallor.

"Come on, Tuff, you're not even trying!" His sister called over as he dropped the log he was struggling to carry. Simply grunting, he bent over to catch his wavering breath. Perhaps she was right, he thought suddenly, perhaps it was poisonous. I could die. I could be dying right now! The thought brought on a wave of dizziness that made him stumble forward.

"Oh, don't be stupid!" His sister scoffed, lugging a large branch over her shoulder. "If you think I'm gonna fall for that again, you've got another thing coming!"

Tuffnut faltered, then gave a sharp, unnatural laugh. "Yeah, no fooling you, sis!" He stood up straight once again and lifted the log, lurching sideways as he did so, but he was determined to cover up his weakness. He was determined not to be sick.

However, no amount of resolve could stop the poison that was slowly spreading through his veins. The pain began deep in his stomach, spreading slowly out through all of his limbs, numbing him. Finally, he could struggle no more, tripping over his own feet and finding that, once on the ground, he could not get up again.

His sister glanced over sceptically, raising an eyebrow in irritation. "Look, I'm not doing all the work, okay? Get up and do something!"

"Sis..." He croaked, the world dipping and spinning, twisting and writhing around him, totally out of focus one second, then clearer than ever the next. The dull aching creeping through every limb was enough to make him cry out in pain, if only he could find his tongue. An abrupt wave of nausea swept over him, and he managed, somehow, to roll over before he managed to vomit all over himself.

When the sickness started, Ruffnut realised that he wasn't faking it to annoy her. He really was sick. She yelled out his name, dropping her bundle of wood and rushing over to kneel by his side. The sister placed a hand on his forehead, then pulled back with a hiss. His brow was scorching, almost too hot to touch, but his skin was pale and sickly, covered in a thin layer of sweat. She took his hand gently.

"It's gonna be okay, Tuff. Just relax, you'll be fine..." There was no weight to her words. Even she didn't believe them. Turning, she clapped eyes onto Barf and Belch, hanging around nervously near the fire-pit. "Barf! Belch! Light that fire!" She called. Instantaneously, they whipped around, Barf spraying noxious, green gas into the wood, and Belch sparked it with practised precision. The fire leapt into life with a loud bang.

Above them, the clouds had gone from powder-white to steel-grey. The storm was upon them, and Ruffnut had no time to get her brother out of the way. She was afraid to move him, in case it made him worse. His almost inaudible moans were rattling her right down to the core. The rain began to fall in hissing sweeps, spattering them with cold, hard droplets that clung to the end of Ruffnut's nose as she peered down for any sign of improvement. A clap of thunder echoed across the island, and the Zippleback retreated into the forest, as though it would afford them some protection from the lightning strikes.

Ruffnut's hand travelled the length of Tuffnut's burning, rain-soaked face, and she uttered a soft noise of dis-belief. She had never seen her brother so sick, not once. A cold or Eel Pox was nothing compared to this. Though his eyes were wide open, staring, unblinking, he saw nothing of the world around him. His breath came in short, sharp gasps, his limbs trembling against his sister's knees. She slumped to the side, unable to look a moment longer, closed her eyes and tried to pretend it wasn't happening, but his tiny, painful moans kept snapping her back to the nauseating reality.

"Stop it... stop making those noises..." She begged, frowning in frustration, but he didn't seem to hear. The only reply was another short gasp. Agonised, she turned back and groaned. There was nothing else she could do. The fire raged behind her, bright and untameable, casting dark shadows against her brother's pale face. She lent down and touched his cheek, brushing some of his unruly hair back out of his eyes.

"Oh, Tuffnut... you're so stupid. I really, really hate you right now." Even as she said the words, she knew she didn't mean them. His eyes slowly closed as he slowly, finally lost consciousness. His head slouched sideways, turning towards her, almost as though he was begging to be comforted. She responded dutifully, dredging up he mother's song from the depths of her muddled memory.

"Hush, little Viking, don't you cry,

Or the Berserker will stab you in the eye,

Don't let the enemy see you afraid,

Or they're gonna gut you with a rusty blade..."

She coughed to clear her throat, her eyes closed, taking a deep, calming breath so as not to choke up as she tried to sing the final verse.

"If that dragon hears your moans,

he's gonna mash up all your bones...

Brother, promise you won't die on me,

I'll get us back, just wait and see..."

It was possible she would have broken down then and there, if her attention hadn't suddenly been caught by a low-flying dragon whooshing straight over her head. She was on her feet in a second, whirling around to face the danger. A Nadder stood behind her, like no dragon she had ever seen. It was completely white, white piercing yellow eyes that glared at her as her rider slid down off her back.

The rider was dressed in pale riding gear, bleached to shield them against the clouds, with a strange mask covering their face. It was strange, made of leather with a face painted on, a hideous, grinning face, baring its teeth in a primeval snarl. As the rider approached, Ruffnut stumbled forward a few steps, pulling herself up to her full height, more than ready to fight with her hands balled into fists.

"Who are you? Don't come any closer!" She yelled. The rider, however, did not stop. More forcefully, she snarled, "You're not touching him, or me. I won't let you!"

"Move aside." The voice was strangely familiar, but Ruffnut forced herself not to be fooled. It could be a trap. She took a deep breath, chest swelling.

"Over my dead body!" She declared bravely, baring her teeth.

"That can be arranged..." The rider's hand flicked up, grasping the edge of their mask. It came flying off onto the ground beside them. Ruffnut's jaw dropped.

It was Astrid.

Congrats to those who guessed right! It was Astrid all along! What will she have to say about the twins predicament? And don't you just love a good bit of twin fluff? I think they're really cute sometimes, and I love it.