The Green Mist

Back during the Gold Rush, there were three brothers who had traveled so far and earned so little, they were in need of whatever gold they could find.

The brothers had heard a local legend of a mountain that had tons of gold in store, and were debating on whether to go or not. The first brother was desperate, and left his companions to set off for the mountain.

When the first brother arrived, it was nearing dusk. He spotted an old abandoned shack, which looked in good shape. He entered the house and found nobody inside. The room was a bed, a chest, and a table with two chairs. He was about to sleep, when he looked out the windows and saw green mist rolling over the hills. Luckily, he had shut the door, but it wouldn't hold against the mist. He moved towards the chest and pulled it away from the wall...

The second brother was worried, since his brother had not yet returned after two weeks. The third brother persisted that he didn't need them anymore and that he was selfish to go alone. The second brother promised that he would return in three days, with or without his brother.

The second brother arrived at dusk, and had not yet seen a trace of his brother. He looked around the hills and stopped, gazing at a cabin. He knew that's where his brother was. He ran for it, entered, and shut the door behind him. His jaw dropped at the sight of his brother lying dead on the ground. He went to his side and felt no pulse. He picked up his brother, and opened the door...

It had been three days. Actually, a week. No sign of either of his companions. Our last character was worried. He decided the same, to go and find his two brothers. Without them he had nothing.

He arrived at the mountains close to nighttime, and still no sight of his brothers. In defeat, he decided to head home, but instead saw a small house at the foot of the mountain. He walked over, and found his two brothers laying outside. In awe, he dragged them inside, and closed the door. He mourned his fallen brothers. He glanced outside. It was night. A green mist was coming for them. He instinctively tried barricading the door. He pulled the chest in the corner of the room... And... BOOOM! The room filled with the green mist. He tried pushing the chest back, but he was already blacking out.

What had killed these brothers was a gas pocket, which poisoned them instantly. At night, the pockets cooled and released gas into the atmosphere, causing the green mist to appear. The source was coming from under the chest, when moved uncovered the gas pocket, killing them instantly.