 Why does the Scorpion leave their signature at each crime?
The third one, who carried a black satchel like a doctor's bag, walked quickly around behind the teller's counter and started filling it with money. Except that in the trunk lid the owner had burned in 'The Scorpion' in big black letters you could see half a block away." Stevenson followed Hastings' pointing finger, and saw again the crudely-lettered words, "The Scorpion" burned black into the paint of the trunk lid. It was in the crank letter's most obvious form; that is, the address had been clipped, a letter or a word at a time, from a newspaper and glued to the envelope. The Scorpion fights crime. Crooks and robbers are not safe from the avenging Scorpion.
 To show that they "took care" of each criminal.
 To show that they "took care" of each criminal.  To scare off other potential criminals.  To show that they were present at the crime.  To help lead the police in connecting the crimes.