He was transported to the Twilight Realm.

...Link was falling through darkness. It wasn't just an absence of light, it was far more than that. Or, he supposed, far less. It was a magical kind of darkness, a presence of anti-light, of Twilight. He fell through the terrifying maelstrom for what felt like hours, but when he finally hit the ground it felt as though the fall had only been for a few feet. He lifted his head to look around, and saw the inky blackness and desolate landscape he recognized as the land of Twilight, realm of the Twili. Zelda had done it! Link turned around to shout to Zelda that it had worked, that he was there, in the Twilight Realm, but when he did he found himself staring at open air: the portal was nowhere to be seen.

Annoyed by this revelation, Link let out a huff, but was surprised when it came out sounding more like a growl. Confused, Link looked down to see the dirt was only a short distance from his face. Turning to look behind him, Link saw for the first time that he'd become a wolf again, the very same form he'd taken during his adventure. Link tried to frown, only to realize the expression was quite difficult to accomplish with a canine muzzle. It made sense, it was the borders of the Twilight Realm that turned him into a wolf originally, but he and Zelda had not planned this, and Link wasn't sure what to do now. The plan was a complete bust: with the portal gone and Link a wolf, there was no way to signal to Zelda what had happened, and Link couldn't put all his hopes into a rescue from her.

So what was he to do now? Link's eyes drifted around his gloomy setting, and quickly darted into an alleyway when he noticed a Twili resident leave their home. Not wanting to be caught as a strange creature from another world, Link headed off towards the palace, darting from safe place to safe place, using his enhanced sense of smell to guide him. There were a few close calls, but before too long Link found himself at Midna's palace, the same place Zant had once ruled over with an iron fist, transforming his populace into dangerous beasts for his amusement.

Once actually inside the palace, Link realized he wasn't quite sure what he was going to do. He knew Midna, that's for sure, but would she recognize him as a wolf? Probably, but what if she didn't, and only saw a Light World wolf running amok in her kingdom? That would be quite bad...perhaps an alternate plan was possible. What if he went to her personal library? She'd told him of it's existence once or twice, the sum total knowledge of the Twili people, and with luck there'd be something there that could help him get home, or at the very least blend in better. What was he going to do now, which path was best?