Day 2,148

The underground was flooded as soon as we found out they'd escaped the trains. The only good thing about an overly paranoid government is that they will have thought of a plan for any and every scenario, no matter how unlikely.

A group of people who'd gone into the underground during the blitz and become lost in a network of tunnels so vast we're still mapping them twelve years later is a highly unlikely scenario. The fact that these people only decided to surface because they were fleeing from leech-like humanoid creatures was something they never factored for.

As with all things though, we adapt. Whether that's to a world without light, a world where we're at the bottom of the food chain or a world we're trying to claw back from leech-like humanoid creatures who are far more intelligent than we ever gave them credit for - we adapt and overcome.

Trapping them on a closed circuit delayed the inevitable and allowed us a chance to study them remotely, occasionally separating a fairly empty carriage and dissecting whatever we found inside. Turns out that under all the mucus, jagged teeth and segmented flesh they're basically people.