After Edward publicly reveals that Hugo has picked a man’s pocket, Hugo flees. Twain describes his flight with an idiom taken from pre-Elizabethan England:
But Hugo did not tarry for the miracle. In a moment he was up and off like the wind, the gentlemen following after and raising the hue and cry lustily as he went.
The expression “to raise the hue and cry” is an idiom that originated in England somewhere between the 13th and 14th century. At one point under English law, if a crime was committed (e.g. a robbery), it was the victim’s responsibility to “raise the hue and cry,” to pursue the criminal while crying out loudly and drawing attention. Onlookers were obligated to join in until the criminal was captured. The word hue here comes from the Old French word, hue, which means “noise.” The expression can refer either to the pursuit or to the cry itself.
This practice actually continued in England until the 19th century (presumably, the hue and cry was abandoned after England’s first paid police force was formed in the same century). The expression has passed into colloquial British speech to refer to any public noise. Twain’s choice to use this phrase likely reflects a desire for realism in this scene. Both the practice and expression would have been in use at the time of the novel’s action.