Another theme could be human nature under pressure. In his short stories, characters are often faced with extraordinary situations, and through their responses, Kneale shows different aspects of human nature, like fear, courage, and the will to survive.
There are often ordinary people who find themselves in extraordinary circumstances. For example, a scientist who stumbles upon a strange discovery and has to deal with the consequences.
Well, it could be that Nigel has some sort of hidden past or a special mission in the story. Maybe there's a mystery surrounding him that unfolds as the plot progresses. But without knowing more details, it's just speculation.
Well, it might focus on the relationship between Jewel and Blu during the pregnancy. It could include their reactions, how they prepare for the new arrival, and the changes in their dynamic.