Well, I think I have now sampled all of the groups of child detectives/adventurers that I have of Enid Blyton (though I am sure there may be more, but I am not really going to go out of my way to locate any other Blyton Books that I don't have in my collection). This group consists of two boys and two girls though the girls don't actually play an active part in the story. They seem to be more along for the ride and to act as the damsels in distress. As for the two boys, Tom and Andy, it appears that Andy pretty much takes the centre stage while Tom tags along to keep Andy company. In fact a bulk of the book revolves around Tom and Andy making their way through a network of caves.
The bad guys seem to be a bit nastier in these books and the children (if we can call them children as they are actually teenagers, not that the concept of the teenager had been developed at the time of writing) are a lot more isolated than in other books of Blyton that I have read. This is the second adventure where they are trapped, this time along what seems to be some very rugged Scottish coastline. In the first book they were trapped on an island and had uncovered a plot involving a fleet of u-boats. In this one they uncover a sophisticated gun smuggling racket, which also differs from other books I read since this seems into involve enemy governments and organised crime. The other books seem to only involve petty thugs (not saying that the two antagonists in this book are more than thugs).
It was an enjoyable, and somewhat quick, read, but then again I can get through most Blyton books in a day, if I set aside most of the day to read them that is. As I also mentioned, the main character in this book appears to be Andy. He is a very cunning individual who works as a fisherman with his father. He doesn't go to school, unlike the rest of the characters in this book, though their private school education does not seem to show through. I also noticed that with this book the children are trapped longer than what their parents expected them to be away, where as most of the other books the mystery is solved and the children freed in less than half a day.
The last chapter was pretty ordinary with the colonel coming and explaining in very simple terms what had happened. The only thing that I didn't understand was that I thought guns where tightly controlled in England, where as it seems in this book that England (or at least Scotland) is being used as a staging place to smuggle guns elsewhere. Also the way they captured the head guy was very dubious. The only clue they had was a button, and they identified the head guy because the shirt he was wearing was missing a button. In reality, that is what is called circumstantial evidence, and one piece of circumstantial evidence will not convict anybody.