It’s the question we writers often get at events: “Where do you get your ideas?”

My standard answer: They’re in the air, like pollen. Ideas for crime novels come at us from all sides. When it happens, it’s great.

A few weeks ago, I got an idea. I didn’t know whether it was a short story or whether it would grow to be a novel. The characters: a man and a woman. They are both living like recluses, away from society by choice. They are thrown together by circumstance.

Then the woman goes missing.

I started making notes and next thing I knew I had more than a dozen pages, exploring just who these two people are and what’s happening in their lives. They both have pasts that are leading them to the present. What happens in the future? Well, I haven’t yet figured that out, or how I’m going to get there. But I do have a setting now. And names for those two people. It’s been exciting to see the plot take shape in the short time these two characters made themselves known.

And apple trees are involved. Go figure.

Then there’s my novella, But Not Forgotten. Several years ago, I attended my 50^th high school reunion. Yes, I’m that old. There was a big poster at the first evening’s event, listing all our classmates who had died, including the year of their deaths and the causes. I looked at the poster and said, what if? What if there was a question mark next to one of those names? What if a classmate disappeared on graduation night and was never seen again? What if another classmate was determined to find out what happened?

I thought about this as I drove my rental car to the airport. Inside the terminal, waiting to board, I took out a notebook and scribbled furiously. By the time I got home, I had my plot and characters and I’d solved the fictional mystery.

Right now I’m working on The Things We Keep, Jeri Howard’s 14^th case. How did this one start? Well, it was the setting. I go to the local farmers’ market on Saturday mornings and sometimes I park in the vicinity of an old Queen Anne Victorian. Someone is living there, but the house is quite rundown. It looks haunted, as a matter of fact.

What if?

The idea pollen started flying. What if Jeri Howard finds a trunk full of bones in the attic? Two skeletons, even. Jeri has to figure out whose bones are in the trunk, how they got there, and who is responsible. Things are getting convoluted and I have a lot of plot to untangle, not to mention characters who are coming to vivid life.

Believe me, I’m having fun with this one, thanks to all that idea pollen in the air.

I have been doing a major decluttering job on my office. In fact, I wonder if it will ever be over. It’s the very definition of ongoing.

Decades, anyway. I’ve lived in this condo for nearly 30 years. And I’ve been accumulating stuff for longer than that. And no, we won’t talk about the walk-in closet that I’m afraid to open for fear of what might fall out.

I confess. I am a paper magnet. Show me a writer who isn’t. We collect ideas for stories and nuggets of research and stash them away like squirrels gathering nuts for winter.

Because I might use that piece of paper one of these days. It’s a plot point, a character study, an interesting setting. Or it’s just the intriguing bit of research I need to bring that scene to life.

Case in point. About fifteen years ago, I clipped a short, intriguing article out of the San Francisco Chronicle. It told the story of wallets found discarded in the heating ducts of an old military barracks at Camp Roberts, wallets with cash missing, but in many cases, personal items such as IDs and letters left inside.

Camp Roberts, which straddles the Monterey and San Luis Obispo county lines in central California, was a military base back in World War II. At the time, it was the largest military training facility around, with thousands of soldiers passing through. The base was deactivated after WWII, then reactivated during the Korean War. Nowadays, Camp Roberts serves as a base for the California National Guard.

As for those wallets, the theory was that they had been stolen from soldiers in the barracks, the valuables taken. Then the thieves tossed the wallets into the heating ducts, where they were found decades later, when the building was torn down.

A National Guard officer at Camp Roberts was taking steps to see if he could locate the wallet owners, using what papers remained. Later articles outlined some success in doing that.

I clipped that article out of the newspaper and kept it on my desk for several years. I was sure I would use it, someday. I was right. Those stolen wallets at Camp Roberts turned out to be an important plot point in Bit Player, a Jeri Howard novel.

One newspaper article leads to another. In fact, it led me to the Bancroft Library at Cal, where I looked at the Camp Roberts newspaper during the war years. I found out what movies were playing at the base theater and what a fried chicken dinner cost at a local restaurant. And the cherry on top? Bing Crosby and his band played a gig at Camp Roberts at the time I was writing about. That’s just the sort of detail I love, one that adds flavor and spice to my writing. Of course, that mention of Bing wound up in the book.

I used to clip articles out and leave them in folders, part of a work in progress. I still get vital information for my plot from various newspaper. Though these days, I don’t save the print copy of the article, Instead, I save the URL, or cut and paste a copy into a Word document. Or the pertinent piece of paper can be scanned and saved electronically.

Much less clutter. Paper clutter, anyway. Then there’s digital clutter, which is a topic for another day.

My work-in-progress is a Jeri Howard novel, titled The Things We Keep. In this case, the things that have been kept are bones.

Jeri, my Oakland-based private investigator, is off-duty on a Saturday in October. She’s helping friends inventory the contents of an old house in Alameda. Up in the attic, she pries open an old footlocker to see what’s inside. She finds herself looking down at a skull and a jumble of bones.

Whose bones? How did they wind up in that attic? And why?

It’s my job as a writer to put flesh on those bones.

Each book gets off to a similar start. I have an idea and I go from there, butt in chair and fingers on keyboard. A structure emerges, with a timeline that gets revised over and over before I reach the end.

With each new project there are familiar characters—Jeri, of course, and her family, friends and associates. And there are new ones that give life to the story and setting. At the start, those characters are stick figures—bones, if you will.

Right now, I’m working on a section of the book where Jeri is looking for information on a musician from the 1960s who went missing decades ago. She’s talked to his ex-girlfriend, who seems to be an unreliable source, so much so that Jeri feels the need to get another perspective. She searches out his friend from the old days, when the two men were playing guitar in a rock band. He gives Jeri another version of the missing man’s past and disappearance. Then the old guitarist tells Jeri she really should talk with HIS former girlfriend.

That’s the scene I’m working on now.

What do I know about HIS former girlfriend? Well, not much, at first. I hadn’t even been planning on her as a character, until her ex the guitarist brought her up in conversation. Once she appeared on the scene, I couldn’t even decide on a name I liked, but finally chose one—Anita—that works for now.

I had the bones and gradually I’ve been adding flesh.

Let’s see. Anita is the former girlfriend of a guy who was a musician in San Francisco in 1969, when they all hung out together in the Haight. Probably a hippie, back in the day. Now she’s an old hippie. In years, anyway. I know she left San Francisco and lived in Mendocino for a while. Married? No, never did. But she has a daughter.

She doesn’t live in Mendocino now. She migrated back down the coast to . . . Bodega Bay? No. Point Reyes Station? Yes, that works. It’s one of my favorite places and I’ve been there plenty of times, walking the streets and exploring the shops and restaurants. I can see the storefronts on the main drag even now. And taste the morning buns from the Bovine Bakery.

Besides, it’s really easier—and more interesting—if Jeri Howard can go interview people face-to-face, and that small town in western Marin County is an easy drive.

Aha! She makes jewelry. In a gallery? No, a workspace created from the detached garage at her cottage. It’s a small but comfortable space where Anita brews herbal tea. And she has apples in a ceramic bowl. I can smell them.

Anita sells the jewelry at a local gallery. What kind of jewelry? What does it look like? I’m thinking lots of colorful ceramic and silver beads are involved.

What does she look like? I decided she a mane of curly gray hair. In the past, she may have worn hippie clothes that recall the Summer of Love. But not at her current age. As I just discovered, she’s a grandmother now.

Meet Anita, who now has flesh on her bones—and provides Jeri with vital information she needs if she’s ever going to solve this case.

For a writer, there’s something compelling about a crime that’s never been solved, a case that’s still out there waiting for a solution. Since I write fiction, I can resolve the plot myself. Or at least use those old crimes to add mystery to my own writing.

Take the case of the Zodiac Killer. I’m working on a Jeri Howard book, called The Things We Keep. As things are wont to do when you write mystery fiction, a real-life case collides with Jeri’s fictional investigation.

Type “Zodiac Killer” into your search engine and you’ll get millions of hits.

Seven known victims, two of whom survived, are attributed to the Zodiac. The murders occurred between December 1968 and October, 1969. Surviving witnesses described the killer as a man in his 30s.

I say known victims, because there are other murders and disappearances attributed to Zodiac, some going back as far as the early 1960s, others in the early 1970s. However, evidence of his involvement in these murders is sketchy and inconclusive.

The killer sent letters to Bay Area newspaper, taunting the police. Some of the letters included cryptograms. One was solved in 1969. One was solved just last year, after 51 years.

After December 1969, communications from Zodiac were sporadic and sometimes considered spurious. Did the killer stop killing, go somewhere else, or die? The police had a suspect but not enough evidence to charge anyone. That person died in 1992.

The case is still open in San Francisco, as well as the other locations where the Zodiac struck. And the California Department of Justice file is also open.

Robert Graysmith’s book Zodiac, the source of the 2007 movie of the same name, is considered the definitive account of the investigations into the murders.

I’m not going to solve this particular puzzle in my novel, but the Zodiac Killer is certainly a looming presence in Jeri’s fictional case.

There’s another unsolved mystery that has fascinated me for decades. From the same era, as it happens.

On March 18, 1969, Thomas Riha vanished. An immigrant from Czechoslovakia, he was an associate professor of Russian history at the University of Colorado in Boulder. He and his wife Hana were in the process of divorcing. She had recently fled their home, claiming that someone was trying to kill her. When Riha disappeared, the house was full of furniture and the table was set for breakfast.

The authorities supposedly received assurances that Riha was alive and that he’d left of his own accord. Some people claimed to have seen him in the early 1970s, in Czechoslovakia.

But no one really knows what happened to Thomas Riha, with the possible exception of the CIA, the FBI. And maybe a woman who called herself Galya Tannenbaum.

Galya spun many yarns, claiming to be a secret service agent. She also claimed to know where Riha was. She disposed of his house, car and statuary collection. She was also the beneficiary in the wills of two Denver residents. Both the decedents had died of potassium cyanide poisoning.

District attorneys in Denver and Boulder filed criminal charges against her for forgery. When they searched her Denver house, they found a pound of potassium cyanide—and Thomas Riha’s driver’s license and passport.

Galya had several other names, a prior criminal record for forgery and theft, and a long record of mental instability. In June 1970 a judge found her incompetent to stand trial. She was sent to the state hospital in Pueblo, Colorado.

Eight months later, on March 7, 1971, Galya Tannenbaum committed suicide, using potassium cyanide.

For a mystery writer, this is catnip.

I used a variation of the Riha case in my second Jeri Howard novel, Till The Old Men Die. In that book, a professor at Cal State is definitely dead and Jeri gets involved in finding out who killed him.

Of course, I had to have a mystery woman.

Writing that book scratched the itch, but not entirely. It wasn’t the Riha case, with its echoes of Cold War intrigue and the strange woman who used potassium cyanide. It wasn’t the novel I wanted to write at the time. Real life is messy and sometimes it doesn’t have endings, as a good mystery novel should.

The itch is still there. Thomas Riha and the case of the vanishing professor will figure into a novel sometime in my writing future. I’ve already got a plot in mind!