War is usually a time of great uncertainty and upheaval, when reality itself seems to be turned upside-down. What was once normal is now decidedly abnormal, and vice versa. This certainly seems to be the case with Mrs. Drover. London during the Blitz, with its scores of ruined buildings hollowed out by German bombing raids, is almost unrecognizable. And those houses like Mrs. Drover's, which still stand but lie abandoned, have a certain haunted quality about them, which makes them the ideal location for all manner of strange goings-on.
We don't know for sure if the taxi driver really is the ghost of Mrs. Drover's former lover, or whether it's just a figment of her imagination. But the ghostly setting of London during the war certainly provides an appropriate backdrop to Mrs. Drover's mental disintegration. In the midst of war, all the old certainties are crumbling, and with them Mrs. Drover's mind.