What Started Out as a Con Job Turned Into a Plot Point : Hoax: A letter offering to leave a fortune to prominent writers and artists has become both a mystery and an inspiration.

Try to scam a writer and she’ll treat it like everything else: a source of material.

Two months ago, Amy Tan got a letter from Neustadt, Germany. “As an elderly man living alone one thinks not only of one’s past but also beyond one’s own being,” wrote a man whose letterhead identified him as Rainer Bohlke. “In a word, I have a considerable fortune and no heir.”

As an admirer of the novelist’s work, Bohlke said he would be honored to leave all his loot to her. Thanks? He sought none. It was enough just to know “that with this help you would be able to attend to your important work more intensively.”

Tan, best-selling author of “The Joy Luck Club” and “The Kitchen God’s Wife,” was touched. “For a moment, I thought I finally got a letter from someone that didn’t ask for something. Someone who just wanted to give me something.” Not that she was planning to take the money. She drafted a reply turning it down but saying how wonderful it was to be surprised.

Right about then another prominent San Francisco novelist, Isabel Allende, was opening a letter that began: “As an elderly man living alone one thinks not only of one’s past but also beyond one’s own being.”

It was another missive from Rainer Bohlke; in fact, the same one Tan got. “I didn’t take it seriously, but I was polite,” says Allende, best known for her novel “The House of the Spirits.” “My idea at the time was that this was some weirdo who was collecting autographs.” She told him to leave the money to a foundation.

Down in Los Angeles, “Simpsons” creator Matt Groening had received his letter some weeks before. It was the same offer, although this time Rainer did make a little request: “When you would like to give me a little present, please send me a hand-painted Simpsons cartoon.”

Groening was more immediately cynical than Allende or Tan, although he concedes that even he wavered. For about 30 seconds. Then reality reasserted itself.

“Too many people have tried to scam me for gas money in shopping center parking lots,” the cartoonist says.

He wrote on the letter, “Nice try,” added a vulgarism, and sent it back to Neustadt. Then, inspired, he devoted an issue of his weekly comic strip, “Life in Hell,” to the letter and his response.

Groening also mentioned it to some friends of his. “Frank Zappa got a similar letter from Germany offering to bequeath a castle,” he reports.

Tan’s response was more complex. She found out the letter was definitely a fraud after learning through a mutual friend that Groening had recently gotten one as well.

“Instead of being angry or upset or justified in being cynical, I thought it was so funny,” she says.

The result was an ongoing attempt to hoax the hoaxer. “I started thinking, what kind of person would do this? What were the motivations? And what if something completely different happened that he wasn’t expecting?”

Using the pseudonym of “Robert White, Special Agent,” Tan wrote a mock-official letter to Rainer Bohlke. “Please be advised my office is investigating a series of postal fraud complaints, all from writers and artists in California, all traceable to you,” the letter warned.

Bohlke promptly wrote back, saying he had decided to disinherit the writers. “After long considerations I think I give my fortune after my passing to a Organization or another foundation.”

By this point, Tan could be fairly described as obsessed. She created a letterhead that said “Central Bureau of Investigation,” using a friend’s New York address. This letter threatened to unleash the bureau’s German agents if Bohlke did not tell whom he was hoaxing and why, describe how he got the addresses etc.

No response so far. But she’s waiting. And speculating. She thinks, and Groening tends to agree, that this is all too complicated to have been done by some errant teen-ager. Her first letter from Bohlke, for instance, was addressed to a publicist at her American publisher--not a name the average German would have access to.

Tan ended up incorporating Bohlke into her next novel, which now features a character who writes letters to people she thinks has wronged her. The woman offers to leave these individuals a considerable fortune, just to see how they respond. Ultimately, it’s a method of revenge. Tan is even considering changing the title from “The Year of No Flood” to “A Considerable Fortune.”

Maybe she’s received a substantial gift after all.