The clerk in the Chinese grocery glanced at the door, then reached under the counter to pull out an unmarked package wrapped in brown paper.
She carefully slit the thin paper down the side and removed a small, rectangular box that she put on the counter.
"This is very good," she said.
This illicit transaction is occurring in Asian neighborhoods all over Southern California, with people from all walks of life flocking to mom-and-pop stores for a fix of what's inside the box.
It's Chinese chalk and its adherents rhapsodize about its wonders with the fervor of Marv Albert in the fourth quarter. They are even willing to overlook the fact that it's illegal.
The product, sold under names such as Miraculous Insecticide Chalk, is used as a first line of defense against the hordes of ants that regularly plague homes, apartments and offices at this time of year.
You simply draw a line of the stuff across linoleum, concrete foundation or even dirt and the ants simply won't cross it.
"I used to spend hours on my knees by the fridge, killing the ants one by one with my finger," said Jae Rand of the Highland Park area.
"Now I draw a line with the chalk and they don't cross it, period."
The chalk is illegal because it never received the regulatory approval required of pesticides' formulas and packaging.
But many say it is far more effective and pleasant to use than the baits and sprays sold at supermarkets and hardware stores.
"I didn't want to spray that stuff in my house," said high school teacher Nancy Potts of Silver Lake. "I tried things like borax that you hear about and that didn't work."
Potts was not aware that Chinese chalk was illegal and didn't know what was in it. "I just thought it was one of those handy things that came in from other places in the world," she said.
Others were aware that the ingredients in Chinese chalk are powerful. Urban legends surround the product. One popular claim is that the chalk contains DDT, but experts say that it does not.
At UC Riverside, several different varieties of the chalk were tested as part of a project.
"They had a fairly high concentration of pyrethoid insecticide, which acts on the nervous system," said Mike Rust, a professor of entomology.
Rand, a retired nurse, was not surprised. "The chalk is neurologically toxic. You can tell that by the way they die," she said. She described an ant trembling violently immediately after touching the chalk.
One of the insecticides commonly found in the chalk is deltamethrin, which is legally used to control insects on fruit trees and vegetables. A research report by UC Davis and four other universities said that if it's given to mice in concentrated quantities, the animals have seizures and die within two hours.
In the last decade, there have been only two serious illnesses in California due to humans ingesting the chalk, according to the state Department of Pesticide Regulation. Both were children.
"It looks like chalk, so you can imagine how a kid could easily think it was something to play with," said Glenn Brank, spokesman for the Department of Pesticide Regulation.
Compounding the problem is the lack of uniformity in the formula of the unregulated chalk. "When you buy this stuff, you don't really know what's in it, just how toxic it is," Brank said.
The box of Chinese chalk purchased at the Chinese grocery contained an information sheet in Chinese and English, but listed no ingredients. It did include the warning: "Strictly forbidden to be put into mouth."
Part of the product's attraction to consumers is no doubt its low price.
"Seventy-five cents," said the store clerk for a box containing a 3-inch piece of chalk. No tax was collected.
"You can bet there will never be an invoice on that transaction," said Bill Lee, an enforcement officer with the Environmental Protection Agency, which has been battling the importation and distribution of the chalk for several years.
Lee said his enforcement division of the EPA is spread thin and has to concentrate on more immediate health issues, such as how field workers are protected against pesticides and the regulation of disinfectants used in hospitals.
Besides, chalk investigations don't always go smoothly.
"We start looking around [a store] and stuff disappears off the shelves," said David Frieders, director of San Francisco's Department of Consumer Assurance.
"Then every store on the block doesn't have it, either. They make phone calls."
But how do the shops know his people are from his staff?
Frieders blames it on having a limited number of staff members available.
"They get to know who we are."
EPA staffers in Lee's department can't go undercover because they are required to identify themselves as working for the government agency when they go into a shop.
So as long as there is no better, legal alternative product, it's likely that under-the-counter sales of Chinese chalk will continue.
But legal or not -- with ants streaming over kitchen counters, bathroom sinks and pantry shelves -- the product is tempting.
"All I know is that you use the chalk," Potts said, "and the ants just get the hell out."