The Invisible Detective is a series of juvenile adventure novels, written by Justin Richards.
Set in London in the 1930s, the series recounts the adventures of four children, Art, Jonny, Meg, and Flinch, who act as "Baker Street Irregulars" to the detective Brandon Lake, who is known as "the Invisible Detective" as no one has seen more than his silhouetted figure in a darkened room.
They invent the character of Brandon Lake and portray him in weekly consulting sessions in a darkened room.
The Cannoniers are: Art's grandson, Arthur Drake II, is a main character who lives in the present day.
Throughout the books, he learns about the Cannoniers' cases, and in Stage Fright, the loadstone switches him and his grandfather, sending him to 1937 London and Art to the present day.