. . . . "Grave Mistake"@en . "278"^^ . "0-00-231267-0" . "Grave Mistake is a detective novel by Ngaio Marsh; it is the thirtieth novel to feature Roderick Alleyn, and was first published in 1978. The plot concerns the murder of an elderly widow in a nursing home, and involves a rare, and famous, postage stamp."@en . . .