Ramos acknowledged picking up a boy he believed was Etan and bringing him back to his apartment for sex, according to Cohen. But he said the boy declined his advances, so he took him to the subway and waved goodbye.
Three years later, in 1991, after helping secure another conviction against Ramos, federal authorities visited the Patz family again. They were there to deliver the news the family had long dreaded -- that investigators believed their son was dead and they believed Ramos was responsible, Cohen writes.
"The words were not earth-shattering; they weren't saying anything that twelve years into the case both parents didn't already know," Cohen writes in her book. "But now for the first time law enforcement was sitting across the table, telling them that the weight of evidence supported their worst fears."
At the same time, the federal authorities said they'd come to the end of their journey, saying only New York state prosecutors could take the case to court.
They never have.
There have been more milestones since that day in 1991.
In the summer of 2000, New York investigators examined evidence from the basement of the apartment building where Ramos once lived. In 2001, Stan Patz had his son declared legally dead, and in 2004, a judge found Ramos liable for Etan's death in a wrongful death civil lawsuit.
But none of those milestones brought them closer to what the family has long said it wants, barring the return of their son: a criminal conviction.
In 2010, Manhattan District Attorney Cyrus Vance reopened the investigation after his election, something he had promised to do during his campaign.
The promise that authorities were closer to mounting a criminal case seemed alluringly close last month, when investigators flooded the neighborhood and began dismantling the basement where handyman Othniel Miller once had a workshop.
Etan knew the man and had sometimes helped him with odd jobs before he disappeared, Cohen said in an interview on CNN at the time. Authorities had looked at the basement workshop years ago, but never tore up the place as they were doing now, she noted.
Investigators recently renewed their interest in Miller, 75, in part after interviewing him about his connection to the basement. During the interview, a source said he blurted out, "What if the body was moved?"
A few weeks ago, a cadaver dog picked up the scent of human remains. Then investigators began to tear down drywall and cut through concrete in search of clues.
"It was a huge number of resources being thrown into this case," forensic scientist Lawrence Kobilinsky told CNN last month. "It shows you that this case is still alive in the minds, (of) not only the public, but certainly, of law enforcement."
Mike Huff, a retired police detective and cold-case investigator in Tulsa, Oklahoma, who now heads the International Association of Cold Case Investigators, said last month that as he watched coverage of the case, the kinds of details that were emerging led him to believe investigators were confident they had finally come up with a solid line on hard physical evidence in the case.
The big news came over the weekend, when it leaked out that investigators had recovered a chunk of concrete that appeared to be stained with blood.
"I thought, 'Man, this is going to be a slam dunk, they already know the answer to this story,'" Huff said.
Then, suddenly, once again, nothing.
The blood wasn't blood, it turned out. No human remains had been found. Etan's family had to be told that the search had come up empty.
Through his attorney and daughter, Miller has denied any role in Etan's disappearance.
Cases as old as this one can be tough to crack, Huff said.
"The longer it gets away, the more you really have to have hopes and prayers for technology to come into it," he said.
While investigators didn't get the answers they wanted -- again -- Huff says there's still some good to take out of the effort.
"It's a success that 33 years later, somebody is still looking at it," he said.