Tongs

The Tongs were a gang that was based in London in 1909. Mollie Wilkins thought that they might have been responsible for the series of murderers that occurred in 1909. (PROSE: Birthright)

Behind the scenes
According to The Brilliant Book 2012, Jenny Flint was being molested by the Tongs when she first encountered Madame Vastra, who saved her from the gang.