It's set inside one room on a space station on Pluto where the crew are awaiting a spacecraft to pick them up and take them back to earth. Only it is late and all the lines of communication with earth have gone silent. As the crew wait for news with varying degrees of patience and panic one of them says they have seen something outside. It's an alien thing you see (don't laugh). I had to sleep with the light on after watching the film Signs. And it doesn't help that outside the one window at the back of the set it is dark. I'm thinking: if something appears at that window I might freak out.
Then something happens that seems to normalise the situation. Sort of. This is Alistair McDowall after all. It's difficult to explain without giving too much away but it's like someone took a pin to a balloon and pop, the tension is gone. And it never gets it back.