ORDEAL BY INNOCENCE is a good example of Christie's tendency to tweak and twist earlier plot devices and then combine them with different themes to create something new, and here she renders the sort of situation seen in CROOKED HOUSE with an unexpected most-likely/least-likely solution and combines it with her oft-repeated theme of an old, previously solved crime that reopens to affect present lives.
The Argles are an unusual family, composed of wealthy parents and five adopted children--all of whom were drawn from underprivledged backgrounds that continued to affect them well into adulthood. One of these children, Jocko, grew up into a singularly undesirable man; constantly involved in legal scrapes, he is the obvious suspect when his adoptive mother is found with her head bashed in by a poker, and he soon convicted. But two years after his death, a man who could have given Jocko an iron-clad alibi suddenly resurfaces, and the family is suddenly thrown into disarray as the case is reopened.
Christie is, as always, extremely expert in her writing, but ORDEAL BY INNOCENCE proves an extremely mechanical effort without more than one or two memorable characters--still, it offers a typically surprising and memorable Christie solution, and that is saying a great deal indeed. While it does not rank among her finer efforts, both fans and newcomers should enjoy it quite a bit.