This is the fifth and final book in Blyton’s ‘Secret’ series, and the only one of the series I have read. It was originally published in 1953 but the edition I have is the 1966 Armada paperback. Illustrations are by Dorothy Hall and are not particularly inspiring (and the print quality of both text and drawings is not great in this edition). The cover illustration (pictured) is by Mary Gernat and is quite pleasing.

The children are in the familiar Blyton format: twins (of course, though nothing is subsequently made of that) Nora and Mike Arnold and their sister Peggy who is one year older, plus Jack who has been adopted (another recurring pattern) by Captain and Mrs Arnold. More unusually, the party is completed by Paul, the Prince of Baronia, who is at school with Mike and Jack. Paul’s age is not clear, but Jack would seem to be older than both boys as he, unlike them, considers himself too old to wear shorts trousers. Overall, it seems that the children are aged between about eleven and thirteen and we are told that they have already had plenty of adventures together.

The hols begin, as Blyton adventures often do, with the girls awaiting the boys’ arrival and bemoaning the fact that their school breaks up earlier. Once reunited, Mrs Arnold gives them the exciting news that Paul’s mother, the Queen of Baronia, wants the family to find a castle in which her Royal Household and the Arnolds may spend a month or two’s holiday. After perusing details of a surprisingly large number of castles available for immediate rental  they think that the remote Moon Castle might be just the place, so they decide to view it. Driven by Ranni, Paul’s manservant-cum-bodyguard, in his huge blue and silver car that simply ‘eats up the miles’, they arrive at Bolingblow, the nearest town to the castle albeit some twenty miles distant. Other than it being in England, there is no information on where we are, but the later reference to tin mines suggests it might be Cornwall. Luckily there is time for a splendid lunch at a hotel in Bolingblow, but the first hint that things might not go smoothly comes when the waitress tells of strange goings on at Moon Castle.

And, indeed, when they arrive things do seem rather strange. Three sisters are acting as caretakers and seem reluctant to see the castle tenanted. Guy Brimming, the son of one them, would not like it they explain, and when Guy appears on the scene he is certainly very hostile and threatening. Too bad, though, it is not his castle and after a tense standoff Ranni sends him packing. It’s agreed by Mrs Arnold that Paul’s mother will rent the castle, which is to be prepared for them by the caretakers, and Guy must take himself off. Oh, and the tower, which is mysteriously locked and the key supposedly lost, must be opened up. We already have a good idea that this is where Guy is up to whatever he is up to – scientific work according to his doting mother, loafing around according to the Arnolds, no good at all we readers suspect.

But now, in classic Blyton style, Things Go Wrong. Paul’s brothers have come down with measles and are in quarantine, so his family will be delayed. Nevertheless the Arnolds are to commence the rental of Moon Castle. Unfortunately Captain Arnold must test fly a secret new plane (presciently, for a book published in 1953, it seems to be a Vertical Take Off and Landing aircraft) and wants Mrs Arnold to go with him. So the children will go to the castle, but they won’t be alone since Ranni and Miss Dimity (Dimmy), a friend who helps Mrs Arnold with the children, will accompany them. So it’s back in the blue and silver car to Moon Castle, stopping only for lunch at Bolingblow and more dire warnings from the waitress.

This time, the reception from the caretakers is, if not welcoming, then at least acceptant and they assure Dimmy that Guy has left as instructed. On the other hand, the tower is still locked and it begins to look as if the hotel waitress was right, because queer things start to happen. First, it is repeated “TWANG! DONG!” noises, apparently from ancient musical instruments in one of the rooms. Still, perhaps it is just some sort of expansion and contraction process caused by the temperature. But that’s not the only thing. That night, Jack and Mike observe that there is a light in the supposedly empty and inaccessible tower. Could it be Guy? The boys think so, and so do we. So next day the children question Guy’s mother about the key to the tower, but she is very evasive. Unbeknown to her, Jack remains at the castle whilst the others go to Bolingblow and overhears Guy berating her for allowing the castle to be let and telling her that the tower must remain locked for some days more until something (what though?) is finished.

The tower is one source of curiosity, but there has also been mention on a nearby ruined village that the children are keen to explore. Not a good idea, according to the caretakers, since there are deserted tin mines which are dangerous. On the other hand, it might be sensible to get out of the castle where things are getting stranger, with the eyes of portraits glowing angrily and strange hissing noises being heard, and ornaments smashing for no apparent reason. Dimmy’s room is mysteriously re-arranged and a picture crashes off the wall.  A warning, according to Guy’s aunt, that the visitors should leave Moon Castle. But they are made of sterner stuff and the children head off the ruined village.

The village is just as exciting as we would hope, with broken down houses and rusting machinery all around. And then there are the tin mines to explore. Oddly enough, the ladder down a mineshaft is in very good order. It’s almost as if it’s still being used …! Once they have descended, the boys (Jack forbids the girls to come) find a maze of tunnels. Luckily they have brought torches and can have a good poke around, and as they do so they find a peculiar green fire, and glimpse a figure in overalls and a hood who pours something on the fire, which turns purple (this provides one of the few really good illustrations in the book). Then other hooded figures sweep up some strange material, glowing with a colour the boys had never seen before (rather like the unnameable colour produced by the machines in The Mountain of Adventure perhaps).  But it’s time to go home now, which may be just as well because the three boys are now suffering from pins and needles and, what’s more, their watches have stopped.

Back at the castle, the boys’ pins and needles become unbearable, and Guy’s mother surmises that they have been in the mines. Apparently, this was the affliction that had led to the village being abandoned and fortunately she has a lotion which will relieve it. Strange things are still happening at Moon castle, too. All the children’s rooms have been re-arranged whilst in the library books are jumping off the shelves all by themselves. One of them is a history of the castle and its lands, and on inspection it includes some old maps. These show what seems to be a secret passage running from Paul’s bedroom into the tower – the tower that remains so stubbornly locked.

That night the boys do not sleep well because of their pins and needles, and Paul is disturbed by a dark figure in his room, who he takes to be Ranni checking on him. Meanwhile, from their room, Jack and Mike see a shimmering glow above the ruined village, of the same mysterious colour as that which they had observed in the mine. We’ve already got there, but the next morning the children now declare, in classic Blyton fashion, that they are in the middle of an adventure. It’s a rainy day, so ignoring various further queer events the children start the search for the secret passage with no success and when the weather brightens Dimmy insists they go for a swim so the search has to be deferred until night time.

Night comes and after further searching Jack finds a knob in the panelling in Paul’s room (and by this time they have realised that his night time visitor had not been Ranni but a baddie, possibly Guy) which opens a secret door. The girls and Paul are now asleep so Mike and Jack explore by themselves. The door leads to a passage and, eventually, they emerge in the fireplace of one of the rooms in the tower. They leave the room and ascend the main stairway where they come to another room. Inside, angry voices are arguing in, of course, a foreign language. The door is ajar and they can see several men, half of whom are wearing the protective suits and hoods of the figures in the old tin mine. Others are wearing ordinary clothes and one of them is Guy. It seems the men are angry with Guy because he has told them that they have to leave before their work is finished – helpfully, they say this in English before reverting to various foreign languages. Guy says that it is just a matter of leaving temporarily whilst the castle is tenanted. But some of the men think that is just an excuse for him to go behind their backs and sell the results of their work. This work, it now emerges, is to produce a strange, valuable new metal called ‘Stellastepheny’, which is produced by the mysterious fire which is also the cause of the pins and needles illness (it is clear that the overalls and hoods are to protect the men from being affected by this, and Jack surmises that they are made of “some sort of mica”). Guy explains that he had hoped the visitors could be frightened away, but since this hadn’t been successful there is no choice but to suspend operations, and this is agreed.

Now the boys witness an extraordinary event, where the hooded men transfer what we take to be ‘Stellastepheny’ into a glass cylinder, blotting out the whole room in a shimmering radiance in (yes, that’s right) an unnameable colour. Guy exits the room, carrying the precious metal, and the boys follow him. He enters another room, and in a flash of inspiration Jack locks him in. There is some exciting chasing about as the rest of the men depart the tower and disappear into a secret trap door in the stone floor of the room at the base of the tower. The boys place a heavy chest over it, trapping the men and then, rather surprisingly one might have thought, simply go back to bed and have a good night’s sleep.

Even more surprising, the next morning breakfast is forgotten as Jack and Mike tell, first, the other children and, then, Dimmy and Ranni about the night’s events. Dimmy summons the caretakers. Guy’s mother is contrite and tearful, but one of the aunts is defiant, declaiming that Guy is a genius scientist and that, anyway, the owner of the castle has no interest in the mines. She admits that it was she who caused all the queer happenings, using devices invented by Guy. In the past, these had been enough to deter visitors. Ranni is dispatched to get the police who arrest Guy and then the men, who immediately betray Guy, believing that he has betrayed them. It is decided that the caretakers’ fate will be decided by the castle’s owner. Breakfast has been missed but no need to worry – they all depart to Bolingblow for lunch at the hotel. The adventure is over but as Jack says “it was GRAND FUN whilst it lasted”!

Overall, this is an excellent Blyton adventure which stands comparison with the best of her stories. It has many of the familiar elements, including a peculiar family set up and a relative absence of adults, but, unusually, there are no animals, birds or insects. Characterisation of the children is weak compared with the Five or the Adventures  – we really have no idea at all of their personalities or interests – as is the sense of place.  On the other hand, plotting is strong, and the story is genuinely atmospheric in terms of the castle, secret passages and mines. There is a sci-fi element, a little like The Mountain of Adventure, which contributes to quite a dramatic feel, and moments of real tension such as the initial encounter with Guy (who, although rarely present, is a good villain), the scenes in the old mines and the final chase. I like the contrast, evident in many Blyton stories, between the ordinary world of hotel dining rooms and waitresses and, just adjacent, an extraordinary world of adventure. I think this was part of what appealed to me as a child, and I can still feel it when re-reading this book some forty years after I first did so.