Hay's novels usually had a common structure.
They were often set in Cornwall where Hay used to visit, but they also had locations near Birmingham and Liverpool.
The story is usually set at an upper class residence and also includes urban locations.
The lower class heroine finally gets to marry the higher class and elder hero, but there are usually some legal problem over maybe a will and another secondary character comes to an early and unusual death.
Hay was from a Protestant background and her novel's support the role of the upper classes and they frequently have a moral sub-plot.
Foreigners and members of the nouveaux riche are thought, at best, to be suspicious and are usually bad characters.
The novels are noted for their witty and punny dialogue which have been compared to that of the Welsh writer Rhoda Broughton.

However, it would be unfair to stereotype all of Hay's storytelling in this way.
 She wrote many works outside of this genre.
One example is Under the Will, a novella of about 21,000 words told from the view point of three people.
It begins as a romance and develops into an adventure.
 The story starts with Hope Wynne telling of her childhood and her growing up with two boys, one of whom, Charlie, eventually becomes her betrothed.
Charlie and his friend find out about a scheme to work land in Venezuela.
 They sign up for this and leave England with others, believing they have paid for land that will make their fortune.
Hope Wynne is written out of the story at this point.
 When they eventually arrive at their destination, in a remote region of Venezuela, they discover that it has been a scam, and many die of disease.
The two friends eventually make it out of the wilderness, discovering on the way that Charlie has been left a large fortune that must be claimed within one year.
The outcome has a twist that involves a deception, and the money being used to mount a rescue mission for those still stranded in Venezuela.

Hay's writings were initially published as serials in magazines like the Family Herald, at first under the pseudonyms of Mark Hardcastle, Markham Howard or Sidney Howard.
 For a period she used the name M. Cecil Hay, shortening her middle name which was actually Cecilia.
 Many of her works were published as collections of short stories or as a three volume novel.
Novels like The Squires Legacy were published in 60 different issues of the Family Herald in 1875 and this was followed by a three volume novel the same year.
The following year the novel was published in one volume, but by another different publisher.

Her most popular story was Old Myddelton's Money, which was first published in 1875 and it was still in print in 1914.
 Old Myddelton of the title was a very wealthy unmarried man, murdered (supposedly) by his nephew Gabriel, who was tried and convicted of the murder, but escaped dressed as a woman.
This may seem improbable, but the episode was lifted from the real story of William Maxwell, 5th Earl of Nithsdale, who escaped from the Tower of London the night before his execution in 1716 dressed as a woman.
 The murdered man's fortune passed to Myddelton's sister, Lady Lawrence, who is childless, and it is supposed that she will leave the money to various of her in-laws.
 A stranger called Royston Keith arrives in town and takes interest in the affairs of the family, much to the concern of a villainous lawyer who hopes to be one of the beneficiaries.
 The stranger and another potential beneficiary, Honor Craven, form an attraction, and it goes on from there with all of the loose ends being sorted in the final chapters.

Hay died in a house called Bay Trees, East Preston, West Sussex on 24 July 1886 after a fifteen-year career followed by a long illness.
According to probate records her personal estate was worth £272; her sister Susan Elizabeth was named as executor.
She was buried in Highgate Cemetery.
 Her sister, Francis, had died two years previous, in East Preston on 3 July 1884, aged 50.
Their mother died in 1888 and the surviving sister, Susan Elizabeth, passed away in 1908, leaving
Hay's novels usually had a common structure. They were often set in Cornwall where Hay used to visit, but they also had locations near Birmingham and Liverpool. The story is usually set at an upper class residence and also includes urban locations. The lower class heroine finally gets to marry the higher class and elder hero, but there are usually some legal problem over maybe a will and another secondary character comes to an early and unusual death. Hay was from a Protestant background and her novel's support the role of the upper classes and they frequently have a moral sub-plot. Foreigners and members of the nouveaux riche are thought, at best, to be suspicious and are usually bad characters. The novels are noted for their witty and punny dialogue which have been compared to that of the Welsh writer Rhoda Broughton.
However, it would be unfair to stereotype all of Hay's storytelling in this way.  She wrote many works outside of this genre. One example is Under the Will, a novella of about 21,000 words told from the view point of three people. It begins as a romance and develops into an adventure.  The story starts with Hope Wynne telling of her childhood and her growing up with two boys, one of whom, Charlie, eventually becomes her betrothed. Charlie and his friend find out about a scheme to work land in Venezuela.  They sign up for this and leave England with others, believing they have paid for land that will make their fortune. Hope Wynne is written out of the story at this point.  When they eventually arrive at their destination, in a remote region of Venezuela, they discover that it has been a scam, and many die of disease. The two friends eventually make it out of the wilderness, discovering on the way that Charlie has been left a large fortune that must be claimed within one year. The outcome has a twist that involves a deception, and the money being used to mount a rescue mission for those still stranded in Venezuela.
Hay's writings were initially published as serials in magazines like the Family Herald, at first under the pseudonyms of Mark Hardcastle, Markham Howard or Sidney Howard.  For a period she used the name M. Cecil Hay, shortening her middle name which was actually Cecilia.  Many of her works were published as collections of short stories or as a three volume novel. Novels like The Squires Legacy were published in 60 different issues of the Family Herald in 1875 and this was followed by a three volume novel the same year. The following year the novel was published in one volume, but by another different publisher.
Her most popular story was Old Myddelton's Money, which was first published in 1875 and it was still in print in 1914.  Old Myddelton of the title was a very wealthy unmarried man, murdered (supposedly) by his nephew Gabriel, who was tried and convicted of the murder, but escaped dressed as a woman. This may seem improbable, but the episode was lifted from the real story of William Maxwell, 5th Earl of Nithsdale, who escaped from the Tower of London the night before his execution in 1716 dressed as a woman.  The murdered man's fortune passed to Myddelton's sister, Lady Lawrence, who is childless, and it is supposed that she will leave the money to various of her in-laws.  A stranger called Royston Keith arrives in town and takes interest in the affairs of the family, much to the concern of a villainous lawyer who hopes to be one of the beneficiaries.  The stranger and another potential beneficiary, Honor Craven, form an attraction, and it goes on from there with all of the loose ends being sorted in the final chapters.
Hay died in a house called Bay Trees, East Preston, West Sussex on 24 July 1886 after a fifteen-year career followed by a long illness. According to probate records her personal estate was worth £272; her sister Susan Elizabeth was named as executor. She was buried in Highgate Cemetery.  Her sister, Francis, had died two years previous, in East Preston on 3 July 1884, aged 50. Their mother died in 1888 and the surviving sister, Susan Elizabeth, passed away in 1908, leaving 
Mary Cecil Hay