In the novel A Caribbean Mystery, Jonas Parry is a young man working at the Town Clerk's office near St. Mary Mead. Miss Marple mentions Jonas because Arthur Jackson reminds her of him.
According to Miss Marple, Jonas Parry was not "very satisfactory", and Mr Rafiel agrees that Jackson is "not wholly satisfactory either". Later on, when Miss Marple catches Arthur peering through her window, his impertinence again reminds her of Jonas.