Steps to the Gallows by Edward Marston
A scurrilous newspaper has built up a large following by publishing details of political and sexual scandals. It is remarkably well-informed and has therefore created a whole host of enemies. When the editor is killed and the printing press smashed to bits, the Invisible Detectives are hired by the man who financed the production of the paper. He wants the killer brought to justice and the scandal sheet revived. Peter and Paul Skillen find themselves in great danger as they unearth an enormous amount of scandal and corruption before the villains are brought to book.