The day Loki finally went mad, Thor was actually quite a long way from his father's halls and not thinking of anything particularly dark or savage. The thunder god was, for once, at a kind of peace with himself; which was good, because being at peace with his brother at that point would have been beyond a Buddhist monk.
It was another brilliant, clear day in the realm of Asgard, and Thor was watching the falcons. He rather liked them; next to horses, they were one of the few dumb beasts to truly capture his attention. They were odd, aggressive little birds, but they generally kept well clear of the city because they were righteously terrified of the wrath of Hugin and Munin. The female bird was busy berating the smaller male, shrieking at him in high tones. Thor smiled. She reminded him of Sif, chasing Fandral out of her horse's stall. And thinking of Sif -
"Thor! Thor Odinson!"
His pleasant reverie was broken.
"My apologies, my prince. But you must come now."
His father, no doubt. Thor was just working up a good line of reasoning not to fall in line with Odin's summons this time when the look on the guard's face got through to him. The man was white and shaking, his eyes full of horror. Thor rose sharply, the falcons forgotten.
"What is it? Speak now!"
"It - it is your brother- "
And it was.
Thor slammed into Loki's chambers without a backward (or indeed much of a forward) glance, and strode straight into the figure of Hogun, who was staggering backwards out of the doors.
"Hogun! Have you seen my -"
Hogun dropped like a stone, unconscious. His face was marked with tiny dappled burns, as if he had leant over a sputtering frying pan and got far too close. Up ahead, the sound echoing slightly in the high, vaulted ceilings, someone was grunting with exertion, and there were the short, scudding sounds of well-made boots hitting the floor in a rapid tattoo. Cursing quietly to himself and more unsettled by the minute, Thor carefully stepped over his senseless friend and continued deeper into his younger brother's domain.
Loki's rooms were, uncharacteristically, a mess. Loki was (in this as in many things) an oddity amongst most of the young men in Asgard, in that he was habitually neat and conservative in his choices of decoration. His only indulgences to his personality to be seen in his rooms were a predilection for the colour green and more books than were to be found in the libraries of a dozen worlds, all arranged carefully on shelves or in trunks. Loki loved to know things, and he liked to keep his sources close by him. Fandral had often teased him about it. "You love those books more than you love your kin!"
And now his brother's beloved books lay in drifts along the edges of the furniture, piled high and haphazardly as if they had simply fallen all at once, like snow. Torn pages fluttered away from Thor's boots as he advanced, fearless, towards the sounds of conflict ahead.
"Loki!" he called. Perhaps the message had been garbled. Wrong. That was it. This mess was the result of some sorcery gone wrong, that was all. Loki was merely indisposed. A headache, perhaps. The lad was always thinking too much, wasn't he?
"It's some illness, perhaps, my prince," the messenger had said, back-pedalling rapidly after the look on Thor's face had hardened from shock into furious denial.
It's your brother.
Thor couldn't stop the words ringing in his head.
It's your brother. He's lost his mind.
He walked past the ruins of Loki's library and thrust open the inner door. The bulk of Volstagg was crouched on the floor, back to Thor, the huge man's body twitching and quaking as if struck by invisible blows. Thor advanced impatiently: at last, some answers would be forthcoming.
"Volstagg -"
"Thor!" Volstagg's rumbling voice sounded strained. "If you have will, lend me your strength!"
Volstagg, as Thor rapidly discovered, was sat bodily on Loki, pinning the smaller man to the floor. Loki's boots, visible splayed out from under Volstagg's tree trunk legs, kicked wildly, heels hammering on the marble.
"What in Hel's name is going on here?" Thor wondered aloud, bending swiftly to Volstagg's aid. Closer now, and he could see his younger brother's face. Loki's pale cheeks were chapped red with rage, his green eyes glaring glassily, and he was thrashing violently against the Warrior's restraining bulk. "Brother, what is wrong with you? Are you agued?"
Loki spat out a word from behind his teeth, pale lips flecked with foam. The word took physical form, became a coiling, amorphous beast with fangs bared, which lunged straight for Volstagg's eyes.
Feeling as if he'd just been thrown bodily into the waterfall plunge pool in midwinter, Thor grabbed for Loki's shoulders as Volstagg reared back in alarm. His brother's fevered strength was alarming. Loki had never been a serious match for Thor physically: countless wrestling, sparring and lifting matches had established this as fact long ago. But he was quick, and now his thin body was like forged steel wire, flexing and twisting to be free of Thor's hands. And he was growling: wordless and feral noises, like a wild beast in a trap. It was incomprehensible. Where was his brother's clever wit, where were his careful words?
"Thor, knock the sense from him, quickly, before he gets loose!" The third of the Warriors, with Lady Sif at his side, had just appeared in the doorway, breathing hard from running.
"I will not hurt my brother, Fandral, he is clearly sickening with some foul disease!" Thor wrestled Loki back to the floor.
"Thor," said Sif, as softly as she could manage and still be heard over the frenzied sounds of Loki trying to free himself. "You know that isn't true."
Thor's arm abruptly throbbed pain at him as Loki bit into his wrist like a starving wolf, and the numb, shocky feeling of being plunged without warning into freezing water intensified. Sadness gripped him.
"Forgive me, brother," he murmured. "I swear I will do everything in my power to help you."
He drew back his other fist, and punched Loki hard between the eyes. As the god of mischief collapsed back to the ground, his consciousness fled, Thor met Sif's accusing look.
You know that isn't true.
"He is my responsibility," he murmured, and scooped the lolling, lanky body up in his arms. "Fandral, go to my father. I must take care of Loki now."