What is common with many post apocalyptic novels is that they show the stagnation of society and ethics. The human race quickly turns into savages, with no morals and only the fundamental will to survive which is prevalent with most species on earth. Vintage British sc-fi, The Day of the Triffids is no exception.
Bill Masen has woke up from his hospital bed to discover that everyone is blind except him. The reason for this mass blindness was a green tinted meteor shower that nearly everyone saw. It harks back to War of the worlds and even influenced the opening scenes of 28 days later. It also seems that John Wyndham (writer) is being coy in that he is using the triffids as a metaphor for the soviets during that time and the cold war. Indeed it is a cold war book, written at a time of much suspicion and underhandedness. Wyndham himself used the communist "threat" in most of his novels.
SPOILER ALERT: as the book goes on, Bill finds pockets of sighted people and forms groups with them, but these groups quickly turn into gangs which are hungry and fighting for food. At the end of the book, it kind of leaves you guessing whether mankind will pull itself back from the brink or just flicker like a flame and die out. And there is much chance of humans dying out at this time of global warming, Iran and cheese.
Fact: there have been 45000 extinctions in earth's natural history. Thankew.