Never given a real origin or even a hint as to just what he was, Mr. Crime was a spectral being who delighted in following the exploits of criminals, while at the same time whispering in their ear to egg them on as well as giving them suggestions about what act of evil to commit next.
He was also known to do the same thing with various members of law enforcement so they would be more likely to gun down the criminals he had chosen to “sponsor.”
Never seen by anyone in the stories he served as sort of an anti-conscious for the featured criminal. The only people he ever told the truth to were the comic audience whom he often addressed directly.
Mr. Crime was the first of the anthology comic book narrators.