Fog is a classic mystery-thriller by Valentine Williams, one of the masters of early twentieth-century suspense fiction. The novel centers on a mysterious and elusive criminal known only as "Fog," a shadowy figure who operates from the depths of London's mist-covered streets. As a series of daring crimes and baffling incidents unsettle the city, investigators struggle to uncover the true identity of the mastermind hidden behind the veil of secrecy.