Earl Drake is a thief working for an unnamed U.S. agency.
His real name isn't Earl Drake. It is just one of several aliases he has used over the fifteen years spent in a life of crime. During the first book, his name was Chet Arnold. He uses the name Earl Drake throughout the majority of the adventures chronicled in the books since that was the best one under which he was not wanted for any crime.
Drake's life of violence started at the young age of 12 when an altercation with another kid over Drake's cat escalated into a vendetta. Drake showed no amount of beating by his father would stop his sense of justice. Years late, at 18, he had another spell of trouble when two cops, seeking to get a confession for stealing hubcaps, for which he was innocent, resulted in his being severely beaten. Rather than press charges, he opted to take vengeance into his own hand and soon both police officers were 'paid back'.
His life of crime started, according to him, when he watched a friend, a poor black man named Oily Barnes, arrested and convicted of a crime on trumped up evidence. At that point, when he was 19, he decided that playing fair was not the way to go. From then on he earned his living through armed robbery. This life of larceny would continue for the next 15 years.
Then he met Hazel Andrews, the luscious, 6' tall redhead lover who helped change Drake from a confirmed criminal to an erstwhile agent of the government. She would help in several missions and provide the incentive to join in several more.
The exact agency for which Drake worked is not known. He worked actually for a government agent named Karl Erikson who probably was assigned to the Treasury Department. Erikson is often transferred on a temporary basis to other agencies.