Danger looms at all sides

Secret passages and caves, smugglers, a sinister house on top of a mountain surrounded by dangerous marshes, a typical setting for the famous five. Add the fact that they have to keep Timmy hidden since the owner of the place hates dogs and there is enough adventure and secrecy to make up for a great adventure.
Not much of a suprise as the climax of the story goes, it all gradually builds up to the uninevitable end. Sometimes even the five seem a bit dim as wich the deaf servant who is sleeping in times of crisis.
Also better not take too close a look at the monstrous cave at one side where they can only descend by rope-ladder and the entrance by stairs a few yards further in the same bedroom.
All in all another great story from Enid Blyton in her most famous series in a great setting.