Margaret Rutherford stars as Agatha Christie's inimitable spinsterish sleuth, Miss Marple. The film opens with her on jury service refusing to return a guilty verdict. Determined to prove her case, she infiltrates the crime 'scene', a touring theatre company headed by H Drifford Cosgood and, gaining a part in their latest production, sets about solving the case with the help of her confidante Mr Stringer.