Little is known of the life of Josephus Doombie  before his appearance in the public eye in 1941.  He had been a semi-public figure at some point, with public discourse on his theories that atoms could be "compacted", allow items to be reduced in size.  In the Autumn of 1941, Doombie had perfect two sera - one that shrank items and another that restored them to normal size and determined to use his discovery to claim that wealth he had always lacked.  His first target was the Rubinoff Emeralds, a million-dollar collection held by the wealthy John Hartford.  One evening while Hartford was entertaining District Attorney Larry Belmont and his daughter Dian, he displayed the emeralds in his library to impress them.  Unknown to them, Doctor Doombie was watching from outside in miniature size and when they left the library, Doombie used a bow and arrow to loop a thread around the door knob and climb up and through the keyhole.  There he resumed his normal size, seized the emeralds and made his escape.
Hearing a commotion, the diners entered the room to find the emeralds gone.  Realizing no one ordinary could have made the theft, Dian using a radio transmitter to Sandman's vehicle to summon him to the scene.

When he arrives, Dian reveals that she has already cased the scene and found a tiny foot print.  She had read of Doombie's theories previously and suggest she and Sandman pay him a visit.  When they do, Sandman spies Doombie through a window, admiring his ill-gotten gains.  He crashes through the window and Doombie summons his thugs, who engage the hero long enough for Doombie to reach his serum and use it on Sandman, shrinking him to size.  In the meantime, other henchmen had discovered Dian outside and drug her in to the house, where Doombie miniaturizes her also.  Gloating, he leaves the two tiny figures in test tubes and announces his intention to rob a bank.

After he leaves, Sandman and Dian struggle to tip the test tubes over and escape.  The inadvertantly knock over a bottle of nitric acid, which threatens  them but the manage to get over it and find the two sera.  They restore themselves to normal size and Sandman races to the bank.  Caught of guard, Doombie and his men are no match for Sandman who has them largely subdued by the time Dian arrives with the police, who promptly cart them off to jail.  The Rabinoffs are recovered and returned to Hartford.

The final fate of Dr. Doombie on Earth-Two has not been revealed.