Chapter One

"Okay, so remind me - where are we, what are we doing here, and what's with the gas masks?"

"We're on a planet called Sartigona. We're here because the Sartigones - those are the aliens that live here - are being attacked by the Tragilicantis and need help."

"And the gas masks?"

"The Tragilicantis are dumping bombs full of poisonous gas on Sartigona. The gas will kill a Sartigone with one whiff, since the Sartigones are about two feet tall. They're all hiding underground to avoid breathing in the gas, but they're going to starve down there."

"And what about the two of us?"

"Well, Time Lords aren't harmed by the gas, so I'm good to go. It smells nasty to us, though, which is why I have a mask on."

"And me?"

"It won't kill you instantly, but if you're overexposed to it, it won't be fun."

"And that means?"

"Keep your gas mask on."

The Doctor and Rose had had quite a few adventures of the "saving-other-planets" variety, but this was the only time that Rose was a little bit scared. Poisonous gas was a new one for her. She didn't want to know what would happen if she breathed in the gas.

The Doctor, sensing her fear, took her hand. "You'll be fine, Rose. I promise."

"Okay," she said. And, hand in hand, the pair stepped out onto the gas-filled planet.