A photograph of Maxwell Smart which has been retouched with Dorian Gray paint.
A special paint developed by CONTROL lab photographer Felix from a blend of "oils and rare extracts used for centuries by voodoo priests to practice black magic".
When the paint is applied to a person's photograph - adding gray to the hair or wrinkles to the face - the same thing happens to the person physically, causing them to age - potentially to the point of death.
After 10 years spent perfecting the formula, Felix offers it to CONTROL, only to be shrugged of by the Chief as an eccentric.
Seeking revenge, he makes a deal with Lucheck of KAOS to dispose of CONTROL for $100,000 and a plane ticket to Miami.
Agent Carruthers is the first to be affected, dying of old age at 28, but soon all CONTROL agents except Larabee are "old, withered and decrepit" The fact that Larabee is also the only one yet to have his new ID photo taken draws suspicion to the photolab and photographer Felix.
Felix is eventually tracked down at KAOS headquarters and arrested along with Lucheck and Lucheck's henchman Kinsky before he can complete the retouching of the CONTROL agents' photographs. An antidote to Dorian Gray is found in the form of a cleaning solution that removes the substance from the photographs and therefore the aging from its victims.
[Episode #123: "Age Before Duty".]