WASHINGTON (Map, News) - Harriette Walters, the alleged ringleader of the most massive corruption scandal in D.C. history, is my neighbor. Who knew?

I don’t share a fence with Walters. But her modest brick house is certainly in my neighborhood. I drive by her place often, it’s on my regular bike route along Rock Creek Park. I pick up soccer balls for my kid’s team down the street.

So I dropped by yesterday morning and knocked on the door. I didn’t expect to meet Ms. Walters. Prosecutors have charged her with creating fake tax refund checks that she and others would cash. They say the scam had been running since 1989, until it was exposed last year. Feds now say the network siphoned off more than $20 million from the D.C. tax office. Walters is being held in jail without bond. No one came to the door of her home on Oregon Avenue.

But proximity breeds questions, from prosaic to practical to profound: Were her kids in school with one of my daughters at Lafayette Elementary? How did she pull off the scam for 19 years? Where did the dough go?

The cash didn’t go into the outside of her brick rambler at the corner of Oregon and Dogwood, facing Rock Creek Park. It has a screened-in back porch, two-car garage, garden hose neatly rolled up. This part of Chevy Chase, D.C., is not too pricey. Up the street at the semigated Unicorn Lane, where the African-American elite resides, town homes go for seven figures. Walters’ place wouldn’t bring that much, the feds will find should they try and sell it.

How did Walters keep her scam going for so long? The feds have described the hard facts of fake checks to straw companies, but how did she keep her dozens of co-workers quiet? Short answer: She bought their silence.

As one former prosecutor tells me, there are two kinds of hush money: One is a one-time payoff to silence someone who has direct knowledge of a crime; the second comes in a series of small gifts that might be rationalized as generosity.

Walters apparently applied the second variety. She bestowed wads of cash to co-workers for cars and renovations and vacations. Some got gifts of $20,000, “given away like cookies,” according to one investigator.

When was the last time your office mate gave you a brownie and a bunch of $20s?

Which begs the next question: Why did no one tip off authorities? Tax workers had plenty of chances, with an anonymous hotline and anti-corruption training. Tax office higher-ups call it “a willful blindness.” I call it a slow and steady slide toward greed, abetted by a reluctance to snitch, and the building of a wall of silence, akin to the one that protected Marion Barry for years while he was addicted to cocaine.

Finally, where’s the $20 million? The sad fact is that if my neighbor gave it away, feds will never get it back.

Unless it’s buried beneath the house on Oregon Avenue.