Plague

There are many ways to die. Plague is just one of them.
Work on a London tube line is halted by the discovery of an ancient plague pit and, within it, a very recent corpse. A day later another body is found, killed in the same way, also in a plague pit. This victim is linked to the Palace of Westminster, where rumours swirl around the Prime Minister and his rivals.

Time is running out and it's not clear what, or who, is going to survive.