Heroin in MetroWest is cheap, abundant and dangerously pure, but for those trying to control the drug, the battle begins nearly 10,000 miles away.
By the time it reaches local streets, the drug has made a journey that is equal parts Magellan and James Bond.
It crosses oceans and a handful of international borders, and is transported cloak-and-dagger style, sewn into clothes, or packed in secret compartments in cars and trucks.
"They're very sophisticated," state police Lt. Dennis Brooks, the head of the special investigations unit at Middlesex District Attorney Martha Coakley's office, said this week.
"They always adjust to our ways, so we have to be very proactive and use our imagination," he continued. "That's another reason why it's difficult to eradicate the problem. As the technology gets better, it's a constant evolving process of cat and mouse."
Though the impacts of drug abuse -- the deaths, the overdoses, the urban decay and rampant street crime that accompany addiction -- are most painfully felt close to home, the trade has today become a truly international enterprise.
Local users and dealers, however, tend to be at the bottom rung of the heroin food chain, where users deal largely only to support their own habit, police said.
"Primarily what we're dealing with are people who are users themselves who are selling to other users," Milford Police Chief Thomas O'Loughlin said this week. "If you're going to compare it to a real-world business, we're the mom-and-pop retail, as compared to some of the major cities being The Home Depot."
For decades, federal officials say, regions like Southeast Asia and the Middle East -- particularly Afghanistan -- have dominated heroin manufacturing worldwide.
Relatively little of the U.S. heroin supply, however, comes from those regions.
For all practical purposes, the country is split between two sources, South America and Mexico, said Lisa Gil, an analyst at the National Drug Intelligence Center who studies nationwide heroin trends.
A part of the Department of Justice, the Washington, D.C.-based agency studies drug use trends at the national, state and local levels, and provides information to policy makers and law enforcement officials.
"The general boundary is the Mississippi river," Gil said. "(To the) east, it's primarily white heroin. West, it's primarily Mexican heroin."
Though not necessarily white, "white" heroin is a highly refined, highly pure product, most of which is produced by drug cartels in South American countries such as Colombia and Venezuela.
Over the last decade, law enforcement officials said, South American heroin has dominated the market with its high purity and surprisingly cheap price. In some areas, the drug sells for less than $10.
But how does the drug get here?
"The most common method is a courier in a commercial airliner," Gil said. "For the most part, they take international flights. They normally go to international airports in Miami or New York."
Couriers typically carry between one to one-and-a-half kilograms, sometimes in the least likely places.
The drug can be stuffed into condoms and swallowed, sewn into clothing, or hidden in luggage, Gil said. More inventive smugglers have even saturated clothing with liquid heroin, then simply carried the clothes over the border.
Once in the U.S., couriers typically make contacts with mid-level dealers in either Colombian or Dominican criminal organizations, NDIC analyst James Dreier explained.
The heroin is typically cut and packaged by such wholesalers, and picked up by local dealers who transport it to Massachusetts.
"They'll travel south, often in private vehicles, often along I-95," said Dreier, who focuses primarily on southern New England. "They'll pick up a shipment of heroin and bring that back to the Boston area."
To make the smuggling tougher for police to spot, many of the cars used are equipped with "hides," secret compartments which can be packed with drugs or cash.
The simplest, Dreier said, are door panels that can be popped off, while the most complex require drivers to perform a complex sequence of steps -- like stepping on the brake, turning on the rear defroster and signaling a turn -- which opens a hydraulically operated panel.
If they make it back to Massachusetts with the drug, dealers may cut it again, they may simply sell it, or they may sell it to a street-level dealer.
It's there that MetroWest users tend to enter the picture.
"Our heroin here, a lot of it comes from Worcester," Marlborough Police Detective Lt. Arthur Brodeur said. "In most occurrences, users from here will make the trip, and they make a pickup for somebody else."
It's a model most MetroWest police are familiar with.
Though the drug can easily be had throughout most of the state, police say heroin distribution is centered in a few larger, urban areas, like Boston, Worcester, Springfield, Lawrence and Lowell.
"They deal enough to support their own addiction," Davis said. "They make trips and keep enough to support themselves. We haven't found a lot of...out-of-town users coming to Framingham to purchase heroin."
For Shrewsbury Police Chief Wayne Sampson, the proximity of Worcester only makes things more difficult.
"Without any question we are seeing an increase in drug use," he said. "Our concern is we see it getting into the school-age children."
In the past year, he said, police have had several cases involving high school students not only using, but dealing heroin. One case even involved an eighth-grade student.
"It makes it easier for young people to get drugs," he said, of the proximity to Worcester. "I understand the whole distribution system of the drug culture, but my residents could care less if it comes from Boston or Worcester or Hartford, all they know is it's in their community and they don't want their kids to have access to it."