In the novel The Sittaford Mystery, Ronald “Ronnie” Garfield is the nephew of Caroline who lives at cottage No. 4 in Sittaford. Ronald visite, hd her occasionally and during the events in the book he was with her.
As Mr Rycroft, one of the neighbours observed, Ronald has "expectations" from his aunt. As he has very little money of his own, he visits his aunt "to dance attendance", hoping to benefit at some future time from her will. Miss Percehouse being a shrewd woman who knows what Ronald's attentions are worth and she keeps him "dancing". During much of the book, Ronald is often seen being summoned by his aunt and ordered to do so chore or other. Such subservient behaviour did not necessarily endear him to his aunt. Miss Percehouse told Emily that while "Ronnie" is a good lad", he would do almost anything for money. "And he hasn't got the brains to see that I would like him just ten times better if he stood up to me now and again, and told me to go to the devil."
Towards the later part of the book, Emily Trefusis is surprised to see Ronald meeting Jennifer Gardner at Deller's Cafe in Exeter. For her it just shows how complex are the web of relationships among the people at Sittaford. She had assumed that nobody at the seance was related to the late Joseph Trevelyan, yet here she sees Ronald with Trevelyan's sister. Every new discovery such as this forces her to re-evaluate her estimation of the various suspects.
It is only at the end of the book that Miss Percehouse tells Emily that Ronald is the godson of Jennifer Gardner and that he was probably seeing her in order to borrow money.
Ronald Garfield is not featured in ITV's 2006 adaptation of the novel. There is a character with a fairly similar name Donald Garfield. He has, however, a totally different backstory and role in the plot, and is not related to Miss Percehouse in this case.