I tried to research what the signs were for when they should return to Erebor but the only one I could find was about the birds so I made some up.
10 Years Later
It was mere months after Bilbo came of age that the three brothers began to notice something strange was going on with Thorin. He went to many meetings with his various friends and advisors that the boys were forbidden to listen in on. They'd caught words of 'signs' and 'prophecies' but belonging to what they did not know.
"Ori, you get to go to the meetings, what happens there?" Bilbo asked, but even the timidest and most polite of the group wouldn't answer their questions.
"I heard them talking about birds returning to the mountain." Fili revealed one night as they sat on their beds talking before they slept, "You don't suppose..."
"You mean the signs for Erebor?" Bilbo breathed, "The signs that mark when Smaug will be killed?"
"You really think it could be happening?" Kili grinned, "That would be amazing!"
"Yeah but are birds even one of the signs?" Bilbo asked, "I mean, Thorin's talked about the signs before but he's never said what they were."
"Tomorrow we'll ask him." Fili decided then, "Just because we've never seen Erebor doesn't mean we can't know!"
His brothers nodded.
-oOo-
Bilbo had laid down on his bed and closed his eyes only to immediately hear the sound of footsteps casing him to blink them open again. Only much to his surprise he was not in his bed as he had been mere seconds ago, but standing in an unfamiliar place.
Bilbo gasped at the beauty of this place, The floors gleamed green like jewels and every statue and pillar seemed to be coated in gold. With fascination he took in the wondrous underground city, so much like the one he'd grown up in only infinitely more beautiful. He gazed off the edge of an obsidian railing, gazing at the crossing roads below him that seemed to go on forever.
Dwarfs bustled past, not even noticing him, talking amongst themselves. Then a large breeze swooped through him, making the Hobbit turn from the people toward the natural light filtering through several arches. He ran toward the wind, watching in awe as he found himself on a balcony high in the mountain side.
He gave a yelp when several Dwarf guards ran straight through him as if he were a ghost but he soon forgot that when a familiar voice met his ears through the strong wind.
"Balin, sound the alarm."
Thorin.
Bilbo looked in awe.
There was his father, shorter and younger than he'd ever seen him, dressed in clothes far finer than could ever be afforded in the Blue Mountains. There were no grey streaks in his shorter hair and his beard was short and tied with a single bead. He was young, even younger than Bilbo was now, he couldn't have been more than twenty five!
"Call out the guard do it now!" Thorin yelled.
"What is it sire?" Balin yelled over the wind.
"Dragon." Thorin breathed before quickly running back inside and yelling down to the bottom levels of the city.
"Dragon!"
Bilbo felt his heart clench. No it couldn't be. It was impossible! If Thorin was a child and he was in an unfamiliar, beautiful mountain city about to be attacked by a dragon, it could only mean...
"Erebor." Bilbo breathed, "I'm in Erebor."
He didn't have long to contemplate this as a huge burst of fire rained down on him, passing through him harmlessly, but he could still hear the screams of those who were not so fortunate.
With a yell Thorin began gathering troops and lacking any better plan Bilbo followed, terrified. This was a dream! It had to be a dream so why couldn't he wake up!
Suddenly they were in front of the great gate that lead to the city, the door was bulging and breaking, flames slipping through it with every heave. Then, the door broke, splintering with the force of the dragon and Smuag stepped inside with a burst of flame. Bilbo was shaking and as he looked to his side he could see the fear in Thorin's eyes as well.
The dragon smashed through the stone structures as if they were nothing, flames licking the walls and incinerating everything and every one in it's path. He watched helplessly as Thorin was flung into the walls and almost crushed under the beasts taloned feet.
Death and destruction was all around, the air stank of burning flesh and smoke, the Hobbit had never been so frightened. He followed as Thorin and those others still living fled the mountain, out to the burning remains of Dale.
"Run for your lives!" Thorin ordered, his eyes then falling on the large hills to the west. Bilbo followed his gaze and was met with the sight of Thranduil and his Elven army. For the first time Bilbo felt hate coil in his heart, he knew what happened here.
"Help us!" Thorin yelled, his face turning from shock to anger as he watched the Elf king turn away without any remorse.
"Hey!" Bilbo yelled, even though he knew nobody could hear, "You traitor! You traitor! Help them!"
Then there was the deafening sound of a roar and more flames descended from nowhere above him. Bilbo heard himself scream-
"NO!"
Tight arms were suddenly constricting his movements and for a few moments Bilbo struggled with all his might, trying to get away.
"Bilbo! Bilbo, calm yourself! Wake up!"
"...Fili?"
He then realized he was back, in his nightclothes sitting in his bed with his older brothers arms around him and he breathed a sigh of relief and stopped struggling.
"We've been trying to wake you going on fifteen minutes now." Kili breathed as Fili released him.
"What?" Bilbo glanced around, still feeling panicked, afraid that any second the dragon would be back.
"You've been screaming in your sleep." Fili continued looking at him with concern, "You woke us all up."
It was only then Bilbo realized both Thorin and Dis were standing by the foot of his bed as well.
Had it really been a dream? It had seemed to real and the details far too fine for any normal dream, the smell and sights...he could remember it all.
"But, the dragon?" Bilbo questioned, "It was right there I swear it!"
"Dragon?" Thorin spoke up.
"Yes!" Bilbo insisted, realizing how manic he sounded, "It was breaking down the door of the city and the entire place was filled with fire and smoke and all those people were..."
He became aware that he was shaking.
"And the Elves!" he growled, balling his hands into fists, "They just turned away! They had an entire army there on the hill and they walked away without a second thought! They left us there!"
"Calm down, brother. It was only a dream." Kili hushed.
"More than a dream." Thorin cut in seriously.
"More than a dream?" Dis questioned.
"One of the signs the prophets foretold concerning returning to the mountain." Thorin answered, staring down Bilbo as he did, "That 'visions will haunt and reveal'."
"Haunt and reveal?" Bilbo repeated fearfully.
The vision certainly had been haunting, he would never forget it of that he was certain, but he can't think of anything it revealed. He knew all that he had seen previously.
"So we are going to reclaim Erebor soon." Kili spoke with awe. Thorin didn't answer.
"We should all return to our sleep." he replied instead, serious and stony once more.
Nodding, Dis and Thorin left the room and Fili and Kili returned to their own beds, the elder blowing out the candle and shrouding the room in darkness again. Swallowing nervously, Bilbo laid down again and tried to will himself to rest but each time he closed his eyes the screams and fire seemed to return.
He was a fully grown Hobbit for goodness sakes! He shouldn't be scared! But frightened he was and he soon found himself trembling once more, too scared to sleep.
He never did ask how his brothers knew he was so frightened in the silence and the dark. But he was certainly grateful when he felt them both slip under his covers and curl up either side of him like when they were children.
-oOo-
"We are going to take back Erebor." Thorin announced the next day, "At the moment we have a company of ten, Gandalf the Grey has agreed to join us. I will be traveling to the Iron Hills, to ask my cousin Dain for assistance."
"We're coming too!" Kili stood.
"Yeah!" Fili and Bilbo added.
"Don't even speak of it!" Dis snapped, "You are all far too young!"
"I'm of age!" bilbo argued, "By Hobbit standards anyway."
"And Ori was part of those meeting and he's younger than us!" Kili argued, "Thorin's been training us since we could walk! We want to fight for our ancestral home!"
"Your mother is right, this is too dangerous for any of you."
"You'll need a burglar." Bilbo piped up, "You can't just go storming into the dragon's den, you'll need some one to sneak inside and scope it out."
"And you think you're going to be this 'burglar' young man?" Dis questioned.
"Why not?" Bilbo posed, "I'm a Dwarf at heart but I'm still a Hobbit in body, I'm much faster and lighter on my feet than anybody."
"he's got a point." Fili agreed, "And you can't send Bilbo without us!"
"Yeah, we're a package deal!" Kili chipped in, "Where Bilbo goes we go!"
"The dragon is too dangerous-" Throin argued.
"I saw what it can do." Bilbo replied with a serious face, "And I still want to go. Dragons have a good sense of smell and Smaug knows Dwarf inside and out, but he won't know me."
Thorin and Bilbo glared at one another in a silent battle of the wits.
"Fine." Thorin relented, "But you will all have to follow orders."
"Yes, sir!" they grinned.
"Brother you cannot be serious!" Dis argued.
"They have made a fair argument." Thorin countered with a sigh, "And we both know they would follow, even if we forbade them."
"You bring them back to me, you hear Thorin Oakenshield?" She hissed, "You bring all my sons home in one piece."
Thorin's gaze drifted to the three celebrating brothers and then to the ground.
"You know I cannot promise that Dis. But I will promise to try my hardest to do so, even if it costs me my life."
Sorry, I really did mean to start the quest properly in this chapter but Bilbo's vision took longer than I thought.
Coming Soon: The quest begins and Bilbo knows the perfect place for the company to regroup before officially beginning. A place called the Shire, specifically Bag End, which his friend Hamfast owns... :P
I still wanted to do the Blunt the Knives/Dwarfs invade Bag End scene but since Bilbo is one of them another Hobbit has to take his place and who better than Hamfast? :) I Just didn't want to make an OC cause lets face it the fanfics for The Hobbit are full of them.