Gary Stewart woke up “in a different world” Tuesday.

After 12 years of painful research — the past 15 months of which was done in secrecy — the book chronicling his abandonment as a baby and his search for his biological parents finally hit store shelves. But the planned publicity fell through.

“Some friends and I went to dinner last night and I was a little bummed,” the Baton Rouge man said. “Here my book’s at Barnes & Noble and it wasn’t going to sell a copy.”

Then his phone started to ring. New York magazine had the story of “The Most Dangerous Animal of All,” and it was exploding across the Internet.

It’s not your ordinary search-for-the-birth-parents book. The subtitle is “Searching For My Father … And Finding The Zodiac Killer.”

The Zodiac Killer is believed to have killed at least five people in northern California in 1968 and 1969, taunting police through letters and cryptograms sent to Bay Area newspapers. The slayings were never solved.

“I never set out to prove my father was a criminal,” Stewart said. “I wanted to find the man I could throw my arms around and have a cup of coffee with.”

Stewart’s birth mother and father met in San Francisco in 1961. Judy Chandler was 13. Earl Van Best was 27. They dated in secret before marrying in January 1962. Chandler’s mother had the marriage annulled, but the couple took flight, bouncing around North America before being arrested in July.

Dubbing the relationship the “Ice Cream Romance” because the two met in front of an ice cream parlor, the San Francisco press had a field day. One reporter, Paul Avery, was particularly scathing, Stewart said.

Avery would later receive letters from the Zodiac Killer.

Best, dressed as a doctor, sprang Chandler from a hospital where she was being treated for hepatitis in September, and the couple was on the road again. They wound up in New Orleans, where Earl Van Doren Best Jr. was born on Feb. 12, 1963, at Baptist Hospital.

One morning, Chandler woke up to find Best scrounging in her purse, Stewart said.

“He said he was taking the baby to Baton Rouge and he had to get rid of the baby,” Stewart said. “He didn’t let her give me a bottle or even clothe me or put a diaper on.”

Best took the Southern Belle train from New Orleans to Baton Rouge, Stewart said, got off at the station and walked to 736 North Blvd., then an eight-plex apartment building. Best walked up the stairs and left the baby in a stairway landing at about 11:30 a.m. He wasn’t found until five hours later when Mary Bonnette picked up her mail.

The story made the front page of The Morning Advocate.

Chandler left Best immediately, Stewart said, only to have him turn her in to authorities. She retaliated, and both were arrested.

Stewart said Best went to prison while Chandler went to a correctional home for wayward girls. When she got out, Best called her and offered to take her back to Baton Rouge for their baby. She told him to leave her alone, and never talked to him again.

Meanwhile, in Baton Rouge, Stewart was adopted by Loyd and Leona Stewart, and raised in what he called a loving, wonderful environment. He always knew he was adopted, he said, and he always struggled with his identity.

In 2002, he finally found his birth mom and heard her side of the story of his birth.

“I said, ‘You know what, Mom? If that’s what my father did, I don’t think I ever want to find him,’ ” Stewart said. And he left it alone, for a while. But something kept driving him.

“I need to find this man and extend the love and forgiveness I was raised with to this man,” Stewart said.

Chandler went on to marry San Francisco police officer Rotea Gilford, who worked on the Zodiac case, Stewart said. Rotea Gilford died in 1998. Now Judy Gilford, she reached out to her late husband’s police friends for help.

One of them, Stewart said, was Earl Sanders, who was briefly police chief in 2002 and 2003.

They found Best’s name, birth date, place of birth and Social Security number. Then, Stewart said, their contacts in the department cut them off.

“Judy, there are things in Gary’s father’s file that we cannot and will not share with you,” Stewart said the contact told them. Stewart continued with his research, unearthing half-siblings in Austria. He said he begged his mom to ask Sanders for more.

“Please tell Gary to drop this,” Stewart said his mother was told. “What’s in that file is so heinous, it will destroy you.”

Stewart, tired of the dead ends, stopped the search.

Then, after a hot day of grilling out in July 2004, he plopped down on the couch to cool off with some TV. A&E’s “Cold Case Files” episode about the Zodiac Killer was on, and Stewart started watching. When a wanted poster from 1969 flashed on the screen, he said, he let out an involuntary yelp. His son, Zach, ran into the room. Seeing the poster, Stewart said, his son said, “Dad, that’s you.”

Stewart thought there was a closer match. He dug out the picture of his dad and compared. To him, they were the same person. Things began to click into place, he said. The stonewalling from the Police Department now made sense.

“I started out to disprove my theory,” Stewart said. “I didn’t want this to be true.”

He contacted John Hennessy with the San Francisco Police Department and eventually went out to California for an interview and to provide DNA samples. A year later, he said, the crime lab agreed to analyze the swabs. Stewart told Gilford and showed her the form that crime-scene investigators gave him documenting the swabs, and he thinks she went to Sanders and her late husband’s other police friends.

“I think she took that CSI form and went to her friend Earl Sanders and Butler (Harold Butler, another Police Department contact) and said, ‘Gary went around you,’ ” Stewart said.

Hennessy was taken out of homicide as a result, Stewart said, and his father’s file was destroyed. Stewart said when co-author Susan Mustafa requested Best’s records, the San Francisco Police Department told her the files were gone.

“The book involves a bit of the SFPD not wanting to cooperate for a reason that’s the hook of the book,” Mustafa said. “You’ve got to read the book for that.”

“We don’t comment on thoughts; we comment on facts,” San Francisco police public information officer Albie Esparza said Tuesday. “If he has any factual information, he needs to call detectives.”

Esparza said he could not comment on any DNA samples Stewart may have given as the case is still open, and added he had no information about new leads in the Zodiac case.

“You can’t imagine how happy we’d be to have this case solved, since it’s been open so long,” he said. “If anyone has any details, any information is greatly appreciated by Homicide. Any time we can close a case and bring closure to families, that’s what we strive for.”

Mustafa, a veteran true-crime writer who met Stewart and heard his story through mutual friends, said she and Stewart have compiled “mounds of circumstantial evidence.”

There’s a scar on his father’s finger, she said, and Zodiac also had a scar. Zodiac mentions organists in his letters, and Best played the organ. Zodiac talked about Gilbert and Sullivan, Mustafa said, and Best was a known fanatic.

“We have chronicled his father’s life,” she said. “In the Zodiac letters, Zodiac gave a lot of clues as to what his lifestyle was like. We have Zodiac’s name in the ciphers,” which she said matched Best’s name.

They also have forensic document examiner Mike Wakshull, who Mustafa said put together a 65-page document comparing Best’s handwriting to Zodiac’s. It’s a match, Stewart and Mustafa said.

Mustafa is convinced Stewart is right.

“I’m a true-crime writer. I have a reputation for research and accuracy,” she said. “If I didn’t believe this, I would never put my reputation on the line for it.”

Earl Van Best died in 1994, choking on his own vomit in a bar in Mexico City, Stewart said. Best traded in antique documents and books, buying them cheaply in Mexico and selling them for a profit in southern California, Stewart said.

“I’m the only visitor ever to his unmarked grave in the poorest part of the poorest neighborhood in Mexico City,” he said.

As for his own journey, Stewart said it’s one he was meant to make.

“I believe I was born to my father and my mother for just that reason. To be placed on that doorstep and to be raised by a beautiful family that gave me faith and hope,” he said.

Loyd Stewart was “my biggest fan,” he said, and Leona, “the proudest Mother’s Day of her life was when I walked in and handed her the first copy of my book.”

And if he could talk to his biological father one last time?

“First thing I would say would be, ‘Thank you,’ ” he said, choking up as he started to cry. “Thank you for leaving me on that doorstep because (the Stewarts) loved me. And I forgive him and that I love him.”

Follow Beth Colvin on Twitter @bethcolvinedits.