Who is lurking in the red mist?

The year I got my A-level results, I began writing a novel. I was very into dystopias at the time. Then I went to university, which knocked my confidence in my creative writing ability. Anyway, I only wrote about 2000 words before I gave up. Eleven years later, I’ve rediscovered it and the writing isn’t as dreadful as I thought. Here’s an extract:

Jean was three streets away from home when the siren shrieked its warning. It was no good pounding on anyone’s door; no one would open so much as an air vent now. She stood, head jerking frantically from left to right, waiting for the red mist to appear. Was it poisonous? Did it smell at all? Perhaps, in her shield-coat, she might be protected for a little while.

A hissing sound seized her attention. It did not seem to originate from any particular direction, but from all around. High up, though.
Jean gasped. The roofs. On the front and back of each roof, the red mist trickled out of single vents. Upon contact with the evening air, each gaseous ribbon enlarged itself into a great nebulous cloud, until all merged into the eerie phenomenon that Jean would normally view safely from indoors. As the air became opaquely red, she held her breath… but of course had to keep breathing.
Her lungs did not disintegrate. Her eyes did not burn. Her skin only felt cold.

Relief overwhelmed her. This mist that everyone was so afraid of was just that – not poisonous, no reason for the government to order everyone inside, into their square, sealed houses. An anti-radiation method? She doubted it. People never wanted to know the truth, did they? They thought they did, but they preferred to believe in the most convenient explanation.

She was just wondering whether to stay where she was for the next hour, or if she should attempt to find her house by feeling her way around, when she thought she heard muffled footsteps behind her. ‘Hello?’ she called tentatively. ‘Is someone there?’

And that’s where the story ends! Maybe I’ll pick it up again some day… I have no idea who’s in the mist, because I didn’t plot it that far! I’ve since learnt that I’ll never finish a story unless the plot is worked out.