"Ordeal by Innocence", originally published in 1958, is one of Dame Agatha Christie's more famous sleuth novels, and already underwent a few screen adaptations. There was a 1984 feature film (starring Donald Sutherland and Christopher Plummer), and the recent BBC mini-series (starring Bill Nighy and Matthew Goode). Very much against the will of the many cynics, the fabulous story also got reworked to fit into Granada's "Marple" series. This series receives quite a lot of hatred because the writers took the liberty to often drastically alter plot aspects and vital story twists compared to the original source novels. Many people don't appreciate this, but I'm an avid Agatha Christie fan, and must state it never bothered me. The changes brought to "Ordeal by Innocence" are quite obvious. As it originally wasn't a Miss Marple novel, our beloved noisy spinster had to dragged in, and it's done by making her the friend/former caretaker of a pivot character.
The protagonist who was the detective in the original novel, Dr. Arthur Calgary, also appears in this version, but his role and he depicts a clumsy, asocial and unworldly "apprentice" of Miss Marple. Of course, there can only be one all-knowing super detective!
I realize I say this about every Christie story, but the plot is brilliant! "Ordeal by Innocence" is a compelling and twisted tale full of loathsome suspects, great settings and very intelligent red herrings. There are great performances all around, including a short but delightful appearance by Jane Seymore, and slightly more blood/violence than in the previous installments.