THE HUM OF HAIR DRYERS and the clatter of conversations in both English and Vietnamese washed over the woman as she opened the door at Fountain Hair & Nails. Sandwiched between a dry cleaner and a barbershop in a small strip mall, the salon was right off a main road in Fountain Valley, California, a sprawling suburb not far from Disneyland. It is one of those places where everything seems pleasant enough but nobody stands out, which made it a perfect stopping place for the fortysomething woman and the gruff-looking elderly man behind the wheel outside.

Smiling politely, the woman said she didn’t have an appointment and asked whether anyone was available to color her hair. She was pressed for time, she said, her husband waiting impatiently in the car. She held up a package of blond dye she had purchased. The salon was filled with customers, but the owner, Kim, smiled and steered her toward an empty chair. Did her husband want to wait inside? No, thanks, said the woman. He stayed in the car, facing the shop’s large plate-glass windows, keeping her in sight the whole time. The woman made little conversation, paid cash — $16, plus tip — then slid into the passenger seat, and they were gone.

Nothing about the January 2000 visit seemed remarkable to the salon owner until FBI agents showed up a couple of weeks later flashing wanted posters. The agents had been alerted by a customer who watched America’s Most Wanted and recognized the couple as Whitey Bulger and Catherine Greig.

It wasn’t the first sighting of the Boston gangster and his girlfriend, nor would it be the last. For five years, the FBI had been fruitlessly searching for Whitey, who was now facing 19 murder charges. It would take 11 more years — and millions more dollars spent on the manhunt — before agents finally arrested him in Santa Monica, less than an hour’s drive from that salon. “We were looking for a gangster, and that was part of the problem,” retired Boston police detective Chip Fleming said later. “He wasn’t a gangster anymore.”

America’s Most Wanted would devote 16 segments to the worldwide hunt for Whitey, all in vain, for he had transformed into the grandfatherly Charlie Gasko, and nobody recognized him — not even some of his Santa Monica neighbors who had relocated from Boston and knew Whitey Bulger by name and repute. Whitey had a reputation for brutality back home, but in California, he and Greig became known as just another pair of amiable retirees who stopped to pet dogs and cats during their daily walks. They strolled to Santa Monica Pier, Palisades Park, or past the upscale shops on Montana Avenue, where it was not unusual to spot celebrities. Often they headed to the Third Street Promenade, wandering among the outdoor mall’s designer clothing stores and gourmet restaurants. Street performers danced and sang; fortunetellers enticed passersby.

Whitey and Greig liked to sit on the benches, people watching. They seemed unconcerned about surveillance cameras or that they had made their home just 4 miles from the Los Angeles office of the FBI. The notorious couple was hiding in plain sight. And it was working.

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JAMES “WHITEY” BULGER and Catherine Greig were an unlikely pairing: She was from South Boston but not completely of it. Many of her classmates were happy to go into the military or get a civil service job, something safe and secure with a good pension. But Greig declared in the 1969 Southie High yearbook that her ambition was “to have a medical career.” After high school, she enrolled in a two-year program at the Forsyth School for Dental Hygienists, then affiliated with Northeastern University. She proved very good at it; in her second year, a prominent periodontist and research scientist chose Greig to work in his lab.

While Greig had vowed not to end up a young housewife without a career, she nevertheless married Bobby McGonagle, her first serious boyfriend, when she was 20. The marriage was troubled from the start. When McGonagle was caught in a compromising position with Greig’s twin sister, Margaret, he joked to family members that he had confused the two. They split up in 1973; their divorce wasn’t finalized till 1977, though Greig was by then dating Whitey Bulger.