On a summer day in 2010, Ethan Condon stepped off a Greyhound bus in Atlanta, called his mother, then disappeared.

Athena Curry was said to have walked out of her boyfriend’s Southside home seven months ago and vanished into the night, leaving behind her baby.

Alan Lee Morse set off from Cobb County headed back to his naval base in Bermuda, but never arrived. He’s been AWOL for 22 years.

Condon, Curry and Morse are among the hundreds of people listed as missing in Atlanta. In many cases, relatives and friends have canvassed neighborhoods, questioned buddies and co-workers, set up websites and badgered police, only to be left wondering about their loved ones’ fates.

In the end, all the families can do is wait for answers. Did the person walk away of his own volition? Was he kidnapped? Is he still alive?

“It’s a 24-hour thing for the family, with us always thinking about him,” said Condon’s older sister, Page Pavelich, who lives in Illinois. Condon, who would be 31 now, was addicted to prescription drugs and was heading north to clean up his life, family members said. He was traveling from Florida to Chicago when he stepped off the bus in Atlanta and missed his connection.

“I go from being mad at him to being sad and frustrated,” said his sister. “It’s a lingering cloud over us.”

Tom Lauth, a private investigator who worked with the now-defunct National Center for Missing Adults, said those emotions often grow during the holidays.

“It’s something they can never let loose; it’s like there’s a lost soul within them,” said Lauth. “They are always looking or wondering, no matter how long it is.”

Last year, 161,016 American adults — 5,282 from Georgia — were reported missing to police and entered into the FBI’s computerized system used by the nation’s law enforcement agencies. At any given time, nearly 50,000 adults are “whereabouts unknown.”

In some cases, dementia patients wander off; people go on drug benders. In rare instances, people are kidnapped. Many who disappear, perhaps most, go underground voluntarily, only to resurface later.

The circumstances of each case determine a police department’s reaction. The more clear it is a person has fallen victim to foul play, the more intense the investigation. But what often tempers a police response is the fact that grown-ups are free to go missing if they so choose.

“If you’re an adult, you can come and go as you please,” said Cobb County police Sgt. Lawrence Szeniawski. Cobb has had nearly 300 missing person cases this year, police said. All but an handful have been solved.

“A lot of missing persons cases solve themselves,” said Atlanta police Detective David Stribling, who is half of the department’s missing persons’ unit. “There’s a lot of issues with people gone missing who choose to.”

Each day, Stribling checks databases, jail logs, hospital intake registers and morgues, looking for an easy explanation for a disappearance. Investigators depend on families to supply them with details of the missing persons’ lives: who they hang out with, if they have criminal pasts, if they’ve had trouble with drugs or money. Then they knock on doors, interview friends and acquaintances and check phone records for more leads.

This year, Stribling and his partner have investigated more than 450 cases. About two dozen are still unsolved, he said.

“There are some missing person cases actively under investigation where we have run out of leads,” he said.

Sometimes, cases take years to solve, like that of Sidonia Harmon, a 30-year-old Atlanta woman who, according to family members, had a crack problem and went missing July 9, 1991.

This month, her daughter, Temeka Strozier, called Stribling, asking why her mother’s photo had been removed from the department’s missing persons’ website.

It turns out Harmon’s remains had been found in March 1992 in a wooded area near Campbellton Road. But there was no apparent cause of death and the skeletal remains went unidentified until detectives obtained DNA samples from her family last year and matched them. Police told Harmon’s mother, but not her daughter.

“I never let it go,” said Strozier, who, at 35, is now older than her mother was the last time they saw each other. “Now I know a little, not a lot. I’m looking for more information. She was found only five minutes from my grandmother’s home. My question is, why did it take so long?

“It was part of my growing up, not knowing where my mom was and all this time she was in the hands of the Fulton County medical examiner,” said Strozier, who wants the homicide unit to take up the case.

Aisha Magee has experienced the same uncertainty and dread.

In late May Curry, her 20-year-old sister, disappeared. Police interviewed Curry’s boyfriend and he told them and family members that she left his house early one morning after a fight. That’s puzzling to Magee, who said her sister had no car, no clothes and left her baby behind.

“From that day on, everything goes cold,” Magee said. She wishes police would investigate more aggressively. “There was no cadaver search, no search warrant, no lie detector,” she said.

Stribling understands families are often frustrated.

“We’re trying to do all we possibly can with what the law allows us to do,” Stribling said. “We hear it all the time ‘If it was a rich person in Buckhead, you’d be doing more.’ ”

That complaint is also often leveled at the media.

“When a person of color goes missing, there’s not the same media coverage,” said Derrica Wilson, a veteran police detective from Virginia who co-founded the Black and Missing Foundation, which tries to attract attention to cases involving minorities who disappear. “If the media doesn’t handle it, we’ll help get the word out.”

Lauth, the private detective, said police departments are often overloaded with cases, so it is often up to families to create publicity and push investigators.

“You have to create your own advocacy,” said Lauth. “The more publicity, the more tips. It all goes together.”

Many families are so stunned, they don’t know what to do immediately.

In December 1989, Morse bid his family farewell to return back to duty in the Navy. Days later, a superior called Morse’s father asking where he was. George Morse discovered his son’s plane ticket went unused and that Alan had told a family friend he was unhappy and thinking of going AWOL. The elder Morse went to police, “but they said it’s not illegal for an adult to go missing.” He did not file a police report.

About five years ago, the Navy called, telling George Morse they would not press charges of AWOL against his son. The elder Morse hired a private eye trying to track down his son. He found that his son had visited a friend after leaving his family in 1989. That friend said he took Alan to a bus station. That was his last sighting.

George Morse hopes his son is alive and hiding, still believing he is a fugitive.

“I’d be delighted to find out he’s alive,” said his father. “But I’d be relieved to find out whatever. It’s a heart-breaking story. He’d be a 42-year-old now. He’s been missing longer than he was with us.”

Pamela Papapostolou, Condon’s mother, worries her son will be forgotten by the system, especially since there is so little to go on.

“The police basically said, ‘If we don’t know anything, there’s nothing to look for,’” she said. “There are people who are forgotten. But, until they tell me he’s not here any more, I won’t give up on him.”