In the novel Postern of Fate, Mrs Henderson is an elderly woman who lives at Meadowside, an old people's home located some ten to fifteen miles from Hollowquay. Winifred Griffin directed Tuppence Beresford to her as a resource person as she "remembers a lot about the Parkinsons". Mrs Henderson had told Mrs Griffin, for example, that Alexander Parkinson did not die from some illness but rather from some food during a picnic.
According to Mrs Griffin, Mrs Henderson is older than she is (although Mrs Griffin is reputed to be the oldest person in Hollowquay). Mrs Henderson was the youngest of a large family. She was a governess at one time and then later as nurse-companion with one Mrs Beddingfield who lived at Swallow's Nest. Mrs Griffin did not elaborate if Mrs Henderson actually worked in the household of the Parkinsons.
Mrs Henderson, and the other residents at Meadowside liked talking about old times very much, Mrs Griffin believed they would welcome the visit by Tuppence.