Swallows and Amazons

...we're adding a whole new plot"

That's always a sign that a production is heading for disaster. If you think the book isn't exciting, don't use it; find some other material. If you think you don't have the ability to convey to an audience what you find exciting about it, find another career.

'Swallows and Amazons' works as a book - and still does, nearly 90 years after it was written - precisely because it is concerned only with the children and their doings. No adult POV is included to give us a perspective on the children's outlook, their emotions and imaginative world; we only see what matters to them and we see it with their eyes. This makes perfect sense to children, and it takes adults back to our own childhood when we too found our own fantasy games far more important and meaningful than anything adults did. I couldn't see how a subplot about 'real' 1930s Soviet spies could possibly be introduced into the plot without making the children's pirate adventures and sea battles seem suddenly trivial and, well, childish.

And sadly, that's exactly what happens. Philippa Lowthorpe works hard to create a sense of danger and excitement in the childhood adventure of unaccompanied sailing, and camping on an island, and very nice too. But the effort is pointless when you throw in real gun-toting nasties kidnapping people and chasing them along trains; that just makes the children's 'pirate wars' fantasy look piffling and tiresome.

A real pity. You wonder why they bothered, and why anybody didn't advise them not to.