To Asgard we go
The bifrost was a very sophisticated blend of magic and technology. It had served all of Asgard well for countless millennium, and was not easily damaged. However, there were certain events that could cause it to malfunction. One of those events was suddenly changing the amount of mass being transferred along the bridge.
Loki should have materialized in the domed entrance to the bifrost, directly in front of the gateway. But with Jack's added mass the pair instead materialized at the door between the dome and the bridge, and were immediately blown back onto the bridge itself.
Loki's back slammed into the glittering bridge, stunning him for a few moments. The God of Mischief blinked to clear his eyes, and Hiemdahl's dark skinned face swam into view.
“Are you alright my prince?” The gatekeeper asked, concern in his usually somber voice. A helpful hand was also extended to him, but Loki ignored it as he pushed himself up.
“I would be better if you hadn't tried to blast me back to the palace.” The god of mischief hissed.
“My apologies, prince. I am not yet sure what caused this to happen.”
“Well find out and do something about it.” Loki said in dry irritation.
Heimdahl nodded his understanding and, after recommending that his prince seek out a healer, left to investigate the bifrost's malfunction. Loki brushed off the advice and started making his way back toward the palace. He thought about the strange occurrence. What would have caused the bifrost to react in such a way? He'd gone to and from Midgard many times and this time should have been no different-
The memory hit like a blow from Mjolnir. The image of Jack Frost hurtling toward him, and feeling a hand grip his arm just as the bifrost was activated.
Loki came to a complete stop on the bridge, anxiety bubbling up inside him. Jack had been inside of the bifrost's range as it was activated. Was that what caused the blast? What had happened to Jack? Heimdahl didn't mention seeing him. Did the winter spirit just get blasted back a ways on the mountain top? At the thought, Loki did a 180 and marched back toward the gateway, intent on demanding to be sent back to the exact some spot he'd just left from. The god of mischief took three steps, and found himself being slammed into the bridge for the second time that day.
“Wow, the winds here are a lot harder to ride than they are back home.” a familiar voice sounded from on top of Loki.
“Jack!” Loki cried, relief and anger flooding through him as he struggled out from the tangle of limbs. “What in Odin's name are you doing here?!”
“Exploring!” Jack declared in his annoyingly cheerful way, swinging his staff up to rest on his shoulders. Loki pinched the bridge of his nose.
“Brilliant, simply brilliant. Now we have to find some way of sneaking you back past Heimdahl. It's hard enough for one person to do, much less two. How did you manage not to be seen by him when we arrived?”
“Oh, I didn't land on the bridge like you did. I fell past the edge, so I asked the winds here to catch me. They don't seem to like me much though, so it's kind of hard to ride them. Sorry about crashing into you by the way. Wait, what do you mean sneak me back? I just got here!”
“And now you're leaving here.” Loki tried to grab Jack but the boy quickly leaped back.
“You're going to have to do better than that!” Jack taunted in a sing-song voice.
“Jack, I'm not in the mood for your games. We need to get you out of here!”
“Not in the mood? That's really too bad, because this is the perfect time for a game of tag! You're it, come and catch me!”
With that Jack jumped off the bridge and was caught up in the winds of Asgard. The winds did not appreciate his hitch hiking and tried to buck him off, causing Jack's to swerve and drop through the air erratically. Loki quickly shifted into a raven to chase after him. Unfortunately, Loki was not as used to flight as Jack was and the violent winds quickly forced him back onto the bridge and into his usual form. Despite the uncooperative winds, Jack was still quite fast in the air, and now a ways ahead of the god of mischief. Loki's heart skipped a beat when he realized Jack was making a beeline for the palace. Loki considered teleporting himself directly to the palace to head him off, but he didn't want to lose sight of the boy either. There was no telling when Jack would randomly decide to go somewhere else, and teleporting too much would drain Loki's energy. If that happened it would be all the harder to get Jack back through the bifrost unnoticed.
Loki took off toward the palace on foot, muttering about all the things he was going to do to the annoying winter spirit once he caught up with him.