He had found out that the Blackbird Mine was valuable and wanted to inherit it, and so he met and romanced his scapegoat Gladys. Jennifer's involvement, however, turns out to be a red herring as the murderer is, in fact, Lancelot. Thinking that one of the two MacKenzie children is responsible, Miss Marple and Inspector Neele trace Jennifer Fortescue (Percival's wife) to be the daughter of Mackenzie - something that she does indeed admit, as well as taking responsibility for placing dead blackbirds near Rex at various times to remind him of his past crimes. Miss Marple discovers that the use of the rhyme in the crimes was to point the finger at an old dealing of the Blackbird Mine, in which old Fortescue was suspected of having killed his partner, MacKenzie, and swindled the mine from his partner's family. The older son, Percival, admits that his father was senile and ruining the business. The younger Fortescue son, Lancelot, suddenly arrives from Kenya with his new wife. The other maid, Ellen, was bringing in the washing when she found Gladys' strangled with a stocking, and with a peg on her nose. She knew Gladys to be romantic and gullible. The next to be murdered is a maid named Gladys with whom Miss Marple was acquainted. Marple realizes the murders are arranged according to the pattern of a childhood nursery rhyme, Sing a Song of Sixpence. Going on the only clue, a pocket full of rye found on the victim, Miss Marple begins investigating. His wife was the main suspect in the murder, until she also was murdered, after drinking tea laced with cyanide.

The diagnosis is death by taxine - a poison found as a mixture of cardiotoxic diterpenes in the leaves, but not the berries (darils), of the European yew tree.

When upper middle class businessman Rex Fortescue dies while having tea, the police are shocked.

Joan hickson a pocket full of rye