Psychiatrist Dr. Leonard Samson came to General "Thunderbolt" Ross with a plan to cure Ross's daughter Betty, who had been transformed into a crystalline form through a blood transfusion with the Sandman. Samson had technicians devise a cathexis ray projector that would drain off gamma particle energy and psionic energy from Bruce Banner as he transformed into the monstrous Hulk whom General Ross had long hunted. Samson theorized that as a result of this process, Banner would be cured of the physiological instability that continually transformed him into the Hulk. Hoping to save Betty and to be cured himself. Banner willingly participated in the experiment. The cathexis ray succeeded in turning Betty Ross back to normal, employing Banner's psionic energy.

However, most of the psionic energy drained from Banner as well as a considerable amount of his excess gamma radiation remained within the cathexis ray projector. Motivated by scientific curiosity, and probably by a desire to gain superhuman powers for himself, Samson irradiated himself with the energies remaining within the projector. The result was that the slight, brown-haired psychiatrist was transformed into a massively muscled, green-haired superhuman with gamma-boosted strength. Banner himself seemed permanently cured, but he emotionally broke under the strain of seeing Betty, the woman he loved, being romanced by Samson, and exposed himself to gamma radiation, thereby undoing the cure.

Samson later lost his superhuman physique and power when he took a blast of concentrated gamma radiation intended for the Hulk. However, months later Samson regained his gamma-mutated form and superhuman strength when he was bombarded by intensive radiation from an exploding gammatron, an experimental gamma-ray generator. He has remained in this form ever since. Doc Samson, as he has been nicknamed, has long sought to capture and permanently cure the Hulk. Samson worked as a university teacher during the recent time that the Hulk was traveling through different dimension, unable to return to Earth. But Samson returned to his pursuit of the Hulk once the monster reappeared on Earth.