Deep within the cave, Dr. Rankin constructed a machine that would enable Calvin to permanently retain any ability that he mimicked instead of losing it by moving away from the person. But one night the machine short-circuited every electrical fuse in the surrounding county. As a mob of angry townspeople neared the cave, Dr. Rankin detonated explosives to seal off the entrance. How ever, Dr. Rankin was caught and killed in the blast. The machine was sealed off in a separate part of the cave.

Sometime later, Rankin encountered Vera Cantor with Henry P. McCoy, an X-man known as the Beast. Rankin and McCoy fought, and during the fight, Rankin gained the same degree of agility as the Beast’s. Nearby construction workers, believing Rankin to be a mutant, forced him to retreat.

Shortly thereafter, Rankin found himself sitting near Jean Grey in a cafeteria and found that he suddenly had developed telekinetic powers. Realizing that she must be the X Man then known as Marvel Girl, he secretly followed her to the X-Men’s base, the Westchester County mansion of Professor Charles Xavier. As he neared the mansion, he began to develop powers like Xavier’s, which he used to determine the special composition of Cyclops’ visor and glasses that enables them to block his eye-beams. Rankin rapidly constructed his own visor and introduced himself to the X-Men, supposedly on friendly terms. But as soon as Rankin was certain that he had successfully mimicked their powers, including the wings of the Angel, he donned a costume he had brought, fought the X-Men, and kid napped Marvel Girl. In costume, Ran kin called himself the Mimic.

The Mimic took Marvel Girl to his cave hideout. Since he was now at a great distance from the other X-Men, he had lost all their powers except Marvel Girl’s. He used the eye-beam power he had mimicked from Cyclops to blast his way to the machine, and had just turned it on when the X-Men broke in. The Mimic seized Xavier, who had accompanied the X-Men, as a hostage, and stood under the machine, expecting that it would make his mimicked powers permanent. Instead, the Mimic slumped unconscious. The X Men, bringing Rankin with them, escaped the cave just before the machine exploded. Xavier explained that the Mimic’s father, realizing the trouble that his power of mimicry could cause, had actually designed the machine to remove that power. Xavier then psionically removed Calvin Ran kin’s memory of being the Mimic.

Months later, while he was a student at Metro College, Rankin was caught in an explosion in a chemistry laboratory there. Rankin was uninjured, but the blast restored both his mimicry power and his memory of being the Mimic. Rankin then con fronted the X-Men, and holding over them the threat of exposing their true identities, pressured them into accepting him as a member. Xavier agreed since he knew the Mimic’s powers would be useful against the menace of Factor Three.

The Mimic’s arrogance and combativeness, however, soon led Xavier to dismiss him from the X Men. Embittered, the Mimic decided to use his powers against humanity. Before he left, he saw the Super Adaptoid defeat the X-Men, whom the Super-Adaptoid intended to transform into androids with the power to mimic the abilities of others, as the Super-Adaptoid itself could. The Mimic discovered that he could not mimic the abilities that the Super-Adaptoid had itself mimicked, probably because the Super Adaptoid was a machine, not a living being. The Mimic volunteered to have the Super-Adaptoid transform him into an adaptoid and then join forces to conquer the world. Eventually the Mimic caused an electrical backlash in the Super-Adaptoid that made both of them to lose the powers they had mimicked from others, as well as the Mimic himself to lose his power to mimic. The Super Adaptoid escaped, and Rankin, a better man for his experience, returned to normal life.

But eventually Rankin discovered that his mimicking powers kept reappearing in flashes, becoming stronger and less controllable each time. Once the power returned so strongly that unless Rankin stayed on his guard constantly, he not only mimicked the abilities of others, but also, without intending to do so, drained all the energy from their bodies, leaving them dead. Rankin was panic-stricken, but Vera Cantor, with whom he was now having a romance, had Henry McCoy, now an expert on mutation and genetics, join Rankin at an isolated cabin in Canada. Rankin had discovered that the distance over which his powers functioned was increasing, and that eventually, he might be draining energy from people all over the world without being able to stop himself from doing so. Unknowing, that happened to the Hulk, who found the Mimic’s cabin. As the Beast, McCoy tried to hold the Hulk off, but then Rankin decided that the Hulk gave him the means of making certain of eliminating the menace that the Mimic posed to the world. Rankin held onto the Hulk long enough to drain enough of the Hulk’s gamma radiation into his body to kill him, and then he died.