This is certainly one of the thinner stories to feature Reginald Denny in one of his sleuthing roles. This time "Prof. Graham" must get to the bottom of the killing of a newly appointed police chief who had just set about tackling the corruption amongst his own. There are no shortage of suspects for the crime - it appears that many of the officers had an axe to grind - but together with Claudia Dell's "Diana" he soldiers on. The title does it some favours - it suggests an intrigue or a mystery that the film simply doesn't deliver, but although I still quite enjoyed this simple story, it's really all pretty slow, stage-bound and forgettable.