The problem for Lawson is that he begins to suspect his sister Joan's (Peggy Evans) new fiance Teddy (Philip Saville) is the murderer. He is a writer of detective novels who seems to be very interested and knowledgeable in the case and also has been acting a bit suspicious. Of course there is a twist... though not one you could easily guess.
Although the film is not too exciting, apart from the river chase, it has an interesting investigation involving tides and patterns. The grime and austerity of early Post War Britain is the highlight (in a manner of speaking) of the film.
