The Squeaker (novel)

The Squeaker is a 1927 crime novel by the British writer Edgar Wallace., published in the US as The Squealer in 1928. In the story, an ex-detective goes undercover to find out the identity of a notorious informer who betrays his criminal associates to the police for his own gain.

Film adaptations
The novel has been adapted for the screen several times:
 * The Squeaker (1930 film), a British film
 * The Squeaker (1931 film), a German film
 * The Squeaker (1937 film), a British film
 * The Squeaker (1963 film), a West German film