A/N: This story wasn't meant to be an alternate time line but with the new Thor sequel coming out soon, and my impatience for knowing what happens, it's obvious that my ideas of what happened after the Avengers movie are wrong, but I do my best to keep things honest to the cannon. Also, many thanks to my brightly colored fighting fish, The March Hater.
Disclaimer: I do not own any part of the copyright or licensing. Done for personal amusement, no monetary gain was made.
Impulse
Thor received a nasty shock when he arrived back in Asgard with his wayward brother. He should have suspected something; Loki had never been quite so compliant. As the remnants of the rainbow bridge materialized under their feet Thor could see the Warriors Three and Lady Sif approaching off in the distance. They had come to help escort the 'prisoner.' Thor waved for them to halt their approach some distance away. He wanted to give Loki one last chance to explain himself. Thor wanted one last chance for to find even the tiniest sliver of hope for his brother.
He thought he had prepared himself for whatever harsh words his brother could dish out. However, when Thor removed the restrictive mask from Loki's face, his brother didn't say a word. He merely gazed at Thor for a moment before his mouth curled in to a smile. He looked as though he would burst into laughter, but no sound ever came. Loki's outline started to twitch. Thor grabbed Loki's shoulders in an attempt to support his brother, thinking he'd started descending into some kind of strange mute hysterics. Loki's shoulders held the weight of Thor's hands, but the being beneath them shook and flickered. Realization flooded through Thor as he retreated from the now unstable form. One of the cuffs and chain that bound 'his brother's' hands slipped through his wrist and land with a clatter. With one last great shudder Loki's double faded out of existence, a look of silent, deranged, laughter still on its face.
The only sound that met Thor's ears was the sound of his friends' footsteps as they ran to his side. Stunned couldn't even begin to describe Thor's despair. Sif stepped forward to retrieve the binding from the ground. Thor took it, staring, sudden frustration the likes of which he had never felt before boiled up violently inside him and remained so until he arrived back in New York to relay the news that Loki was still at large. Thor was sure Stark had thought that his world was once again under attack when he landed on his balcony to relay the news of Loki's escape. Even though Captain Rogers and Dr. Banner were out of immediate contact and Clint & Natasha had been sent cross country to a SHEILD rehabilitation facility for some 'down time' Fury wasn't waiting around to pour any available division into picking up Loki's scent. This fight was far from over.