Tocsin is the name of a mysterious woman who surreptitiously sends hand-written messages to Jimmie Dale, the Gray Seal. The messages contain information on crimes, giving the Gray Seal a means of stopping the crimes and/or bringing the criminals to justice. In The Adventures of Jimmie Dale, the first book with the Gray Seal, the identity of the Tocsin remains mysterious until later on, where her identity is revealed as that of Marie LaSalle, who infiltrates the underworld through the disguise of Silver Mag, an underworld figure involved with the Crime Club. She is also described as 'the woman in black'.