The man known as "Junky" Doolb ("Blood" spelt backwards) was an underworld figure who shot Fred Mason because Mason had not delivered rigged gambling equipment to his gang as promised. Although he left a false clue implicating Rudy Seton as the killer of Mason, Dick Tracy realized that "J.D" (Junky Doolb) was the real killer. With the help of Mary X, Tracy captured Doolb in Rudy Seton's nightclub.
Betrayal by TrohsEditDoolb later tried to break out of jail with a gun that had been smuggled in by Jerome Trohs, who posed as Doolb's attorney. However the gun was not loaded and Doolb was killed by police gunfire
- A later Rogues' Gallery entry about Doolb indicated that he had received a life sentence. This is not accurate, as Doolb was killed before going to trial.