Sent to stay with unknown relatives while her parents are abroad, Polly is delighted to discover that 'The Shrubbery' turns out to be the most wonderful house, with an even more wonderful garden.

It's no surprise to Polly that such an enormous garden, full of rare and beautiful plants, needs a full-time gardener to look after it. But Miss Gargoyle doesn't look - or act - like a real gardener at all. And what on earth can have happened to Polly's two uncles, who have been missing for days? With the help of her cousin Harry, Polly sets out to keep a close eye on Miss Gargoyle and soon discovers that something very sinister indeed is going on in the Shrubbery garden!