The Case of the Telltale Tiles

Fellow sleuths. It's time once again to "exercise the little grey cells," as Agatha Christie's Hercule Poirot would say, with a Dickens Station Mini Mystery. You can easily read today's mystery in under 7 minutes, and the resolution in under 6 minutes. That leaves you 2 minutes for your deductions and hypotheses. Child's play. Is it not?

So, test your "little grey cells" against mine with The Case of the Telltale Tiles, A Dickens Station 15-Minute Mystery.