It was on a few years ago, over a few weeks.
I missed the first episode, so I'm not sure what happened but I think there was a train crash which released a secret "something" which froze the people around it.
The bulk of the story was about a few people (from the train) travelling across a deserted country, in search of the person/people who made the stuff.
The usual cliffhanger events happened over the series, culminating in the group finding who they were looking for. Also with the realisation of how long ago the train crash was.
So, from that rubbish description, can anyone name the series and/or anyone that was in it?