Robert Stark is a security consultant.
In the opening section of the first book taking place in 1975, it is stated that Stark was 34 years old and had been an agent for the CIA for nine years, most of that spent in the jungles of Cambodia and Vietnam, When the Vietnam War ended, Stark was transferred to Japan.
It was there that the incident which forced him out of the Agency occurred. When a man he was running was set up for death by the CIA for being a double agent, a decision made without Stark's knowledge, Stark was furious. When the real double agent defected soon after that, Stark knew he was finished with that part of his life.
An expert in the martial arts already, he chose to enter a Japanese monastery to regain his balance and to hone his skills. Three years he lived there until he felt he could again face the real world.
A short time later, Stark met Halliwell, a recently retired Secret Service agent now looking for something to do with the rest of his life. The two hit it off immediately and began to see how their skills could work together. Halliwell-Stark Associates soon became a highly respected security consultancy. Whether it was keeping a client safe or rescuing a soon-to-be client from kidnappers, they were the ones to call when quality mattered.
The majority of the action takes place starting in 1987, twelve years after he had first quit the Agency, making Stark at least 45 years old. He is still in top physical condition and has maintained his martial arts training so that now he is one of the very best in the world in jujitsu.
For a man who had quit the Agency many years before and had no desire to associate with them again, this series is proof that you can run but you cannot hide when they need you.