Mrs MacArthur

In the short story The Herb of Death, Mrs MacArthur is woman, probably a resident of St. Mary Mead mentioned by Miss Marple as a village parallel for the mass poisoning at Clodderham Court. She had sent Mrs Toomie some special bulbs. The cook mistook them for onions and cooked them. As a result, Mrs Toomie's whole household fell very ill. From the context, it would seem that Mrs MacArthur is either a gardening supplier or a friendly neighbour with a gardening hobby.