This non-series book is bleaker in tone than the usual Christie fare, although it does offer a number of typical elements, notably the well-evoked Devon setting and a family which has a number of secrets. Dr Arthur Calgary, a respected geophysicist, has been out of the country for two years, due to his involvement with an expedition to the Antarctic. Had he been in England, his alibi evidence could have saved Jacko Argyle from being convicted for bludgeoning his mother. Filled with guilt, he journeys to the Argyle home to break the news that the young man - who has died in prison - was not responsible for the crime. Assuming that he will be welcomed because he has been able to clear Jacko's name, he is startled to meet a guarded and even hostile response. But the explanation is soon apparent: if Jacko did not kill his mother, who did? Calgary's fresh information creates an ordeal for those family members who, although innocent, must now come under the microscope. The story is well-devised, with a subtly concealed culprit. Overall, a first-rate mystery novel.