Wheelchair-bound master criminal and art connoisseur.
Leadside's connection to KAOS is somewhat vague; a reported meeting with the KAOS department heads turns out to be a planted decoy story.
His acquaintance with Maxwell Smart goes back ten years during which Max repeatedly ruins Leadside's schemes with what Leadside calls Max's "cunning stupidity".
When Max stumbles onto his theft of the $20 million Burlington art collection from the National Museum it is the last straw and Leadside vows that he will put an end to Max's interference once and for all in three phases: First, he will escape, second he will destroy CONTROL and, third, he will kill Max.
He accomplishes the first easily enough when Max becomes distracted after jamming his foot in a cuspidor. He then "destroys" CONTROL by virtue of the sabotage of the computer known as ARDVARC - the brains of CONTROL.
Finally, he invades Maxwell Smart's apartment, improbably by jogging in clad in gym pants before settling into a wheelchair pre-positioned by his assistants Norman and Kelley. He explains that although he can't walk he can run, revealing that the injury to his spine is "a unique one" enabling him to move forward as long as he maintains velocity but if he tries to stand or walk he collapses. In this way, he was able to get past the CONTROL agents guarding the building because "they were looking for a man in a wheelchair".
Leadside then indicates that "Phase 3", the killing of Max, will be by means of a sword duel. During this, Norman moves his chair forward and back at Leadside's direction until, going back too far, he falls out of the window. Leadside mourns the loss revealing that his mother "gave" him Norman, implying a fraternal relationship, but it gives him the impetus to continue. With Kelley now propelling his chair, Leadside thrusts out his sword and hurtles toward Max, only to see him sidestep him at the last minute and open the front door through which Leadside passes. Max closes the door behind him and thus does not see but can only hear the tremendous crash.
Leadside is taken to the hospital where he survives surgery but, as Max says, "it's going to be a hard road . . . he'll never run again."