Line Engaged is a 1935 British, black-and-white, thriller directed by Bernard Mainwaring and starring Bramwell Fletcher, Jane Baxter and Arthur Wontner.
Eva Rutland (played by Jane Baxter), the wife of caddish Gordon (Leslie Perrins), is in love with David Morland (Bramwell Fletcher), a successful novelist.
David's father, an Inspector (Arthur Wontner) gives his son a cast iron murder plot.
Later, when Gordon is shot, it seems David has fulfilled his father's hypothetical musings.
You can help Wikipedia by expanding it.This article about a 1930s thriller film is a stub.