Like a number of writers little known a century later, Mrs Barclay was a highly popular novelist whose work included her debut romance The Wheels of Time and the bestselling The Rosary. The Times obituary favourably recalled her work,which praised her ability to tackle themes of romance and religious feelings in a way that dispensed with Victorian piety yet retained moral integrity:
Her death removes a figure as well known ten years ago to large sections of the novel-reading public as Charles Garvice, Marie Corelli, or Ethel M Dell. Her most popular book, "The Rosary," enjoyed a circulation of vast dimensions, and made friends of the author in homes all over the land.
It was one of the secrets of her success that she managed to be entirely sincere, and yet to infuse into an atmosphere which many people regard as narrow a kind of repressed excitement.
A writer who appealed to and won the affection of so many of her fellow country men and women is no negligible quantity. Indeed, there is reason to think that Mrs Barclay understood the tendency of her age better than many contemporary novelists whose technical skill exceeded her own. The way in which she blended passion with the spirit of pilgrimage was distinctly post-Victorian.
- Death of Mrs Barclay: a loss to millions of readers, The Times, March 11, 1921
The Mistress of Shenstone tells of the young and beautiful Lady Myra Ingleby, who goes for a rest cure incognito in Cornwall after the death of her husband in some unnamed military adventure at "Targai", somewhere in the Middle East.
"You know perfectly well that Lord Ingleby volunteered for this border war because he was so keen on experimenting with his new explosives, and on trying these ideas for using electricity in modern warfare, at which he has worked so long."
(Does she really want to be married to this guy? Anyhow...) In Cornwall, her life is saved by a young man called Jim Airth, who helps her climb a cliff after she falls asleep on the beach and is cut off by the tide, and the two fall in love and become engaged. Jim, however, doesn't know that she is Lady Ingleby; and she doesn't know that Airth was the man who accidentally killed Lord Ingleby by prematurely detonating a mine. This naturally enough places a tension on their relationship, with a further twist when a telegram appears to indicate that Lord Ingleby is still alive, and there are also class issues (eventually resolved when it turns out that Jim Airth is himself an aristocrat going incognito).
Some of the book is fairly silly, such as Lord Ingleby's dog that gets vibes of his death and dies in sympathy, and also reflective of the prejudices of its time (for instance, the idea that the protagonists must be of the same class for a proper resolution). But it's well-plotted and well-paced, and not at all a bad read; it was filmed in 1921 (see IMDb).
Here's the full book at Project Gutenberg - E-text No. 26235 - and here are the chapters featuring the beach and the cliff climb: In Horseshoe Cove / Jim Airth to the rescue / "Yeo, ho! We go!" / 'Twixt sea and sky.
Many of Mrs Barclay's works are on the Internet Archive (see creator:"Barclay, Florence L. (Florence Louisa), 1862-1921") as is the subjective, but nonetheless interesting, biography by one of her daughters, The life of Florence L. Barclay: a study in personality. There's more biography, and some works, at Literary Heritage West Midlands; as the commentary says, some of her shorter works - such as "My heart's right there" - are morbidly patriotic by modern standards. Contrary to the now more popular anti-war writers and poets of World War One, Mrs Barclay (like Jessie Pope) was distinctly jingoistic at times.
It's a righteous war, my girl; and every man who fears God and honours the King, should be up, and out, and ready to do his share; and every woman who loves her home, must be willing bravely to do her part, by letting her man go. And if she has to hear that he has given his life, she must stand up, brave and true--as a soldier's wife or a soldier's mother--and say: 'God save the King!'
- from My heart's right there