In The Invention Of Murder : How The Victorians Revelled In Death And Detection And Created Modern Crime (2011), Judith Flanders makes a passing reference which, though brief, has me eager to read the novel in question:

In 1860, in The Trail Of The Serpent, Mrs Braddon had advanced her plot through Sloshy, the adopted child of a mute policeman

Come to think of it, I may not bother to read the book itself, but simply adopt the characters for my own use. Sloshy! The mute policeman! They shall live again at Hooting Yard!