Over two decades ago, Jonas Harrow was disgraced as a surgeon and expelled from the medical profession for unorthodox experiments. Happening upon a near-dead criminal in the
Bowery, Harrow, entertaining half-hearted hopes of redemption, cybernetically restored the criminal, who became the gangster
Hammerhead. Harrow slid deeper into underworld research, eventually seeking mind-controlling technology. In the present day, Harrow enhances criminals to superhuman status for a fee. When Hammerhead rises to prominence, Harrow observed his ex-patient's battles with
Spider-Man, whom he perceives as a challenge. He enhances another criminal,
Kangaroo (Frank Olver), who ungratefully scorns Harrow's schemes. Harrow continues providing services to villains like
Living Laser. When
Will o' the Wisp seeks to have his powers removed, Harrow implants a surgical device to extort him into theft. When the Wisp rebels while fighting Spider-Man, Harrow's device temporarily dissipates him. Using stolen information, Harrow develops a "variator ray" to control human emotion. By now obsessed with Spider-Man, he tested the device on
J. Jonah Jameson, who has a nervous breakdown. After Spider-Man locates and destroys the ray, Harrow is imprisoned in
Ryker's Island. Harrow accepted a
Roxxon Oil contract to create synthetic automated soldiers; to this end, he extorts industrial crimes from Will o' the Wisp. Surreptitiously seeking Spider-Man's help, the Wisp instead encounters Spider-Man's clone
Ben Reilly, who removes Harrow's implant. When Harrow releases
Dragon Man from custody, Reilly and the Wisp follow and destroy Harrow's base. Jonas Harrow is hired by the
Hood to take advantage of the split in the superhero community caused by the Superhuman Registration Act. When the Hood is defeated by the New Avengers and loses his powers, Harrow attempts to use a power drainer he created as a bargaining chip to replace the Hood among
Norman Osborn's
Cabal. The Hood soon returns, having gained new powers from the
Norn Stones, and blasts Harrow's head off with a magically-charged bullet. ==Skills and abilities==