In a room tucked away on a floor where the elevator stops only with a special key, a 10-member squad known as Group 9 is a few hours from launching an undercover mission to take down a band of gunrunners.
The agents are part of the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives, which operates out of a low-profile office building on the far outskirts of Houston.
The agency's name is not listed on the building's directory, and the reception area has bullet-resistant glass and other security features.
It is not a secret that the agency has drawn plenty of enemies as it has gone up against street gangs, militia members and outlaw bikers.
But nowadays the ATF Houston Division -- the agency's largest division in the United States -- has a primary mission of stemming violent crime and the flow of guns from here to Mexico's drug cartels.
Houston and the surrounding area is the marketplace of choice for the cartels, which are arming themselves in an ongoing war with other gangsters as well as with government security forces.
Houston remains the number one point of origin for guns that are recovered from the scenes of organized crime murders and other mayhem in Mexico and are successfully traced back to where they were first sold over the counter, according to the agency.
Making matters even more complex, more than 1.1 million customers in Texas so far this year have requested government permission to buy firearms -- a record pace for the state -- and Texas already has more gun dealers than any other state in the nation.
Through it all, the agency has remained lean compared to peers such as the FBI or Immigration and Customs Enforcement, and remains outgunned in many ways in this state, where guns are a way of life and weekend sales are so large they are regularly held in sprawling convention centers.
There are 67 agents and 25 civilian investigators, as well as numerous analysts and support personnel, assigned to the Houston area.
By comparison, there are approximately five times as many FBI agents as ATF agents based in Houston.
"We are looking for the needle in the haystack, and the haystack is all the gun purchases," said Todd Reichert, an assistant special agent in charge of the Houston division, which in 2013 has worked cases from here to the Mexican border, as well as in Latin America and the Caribbean.
There are 1,612 licensed firearms dealers in the Houston area, a higher number than anywhere else in this state.
As a result, there are more people with more access to guns in Houston and the surrounding counties than anywhere else in the United States, according to the ATF.
Firearms hardly raise an eyebrow here in the metropolis, where most gun stores tend to blend into strip centers with restaurants, book stores, smoke shops and bakeries.
There are exceptions, such as the Carter's County gun store that features a shooting range out back, or the upscale Athena Gun Club, with an air-conditioned, 26-lane shooting range with a VIP Club that includes a gun valet.
They stand out.
"I couldn't see it being any other way," said Jim Pruett, owner of Jim Pruett's Guns & Ammo. "I love Texas."
Seized guns tell stories
The ATF isn't always popular in this state, where people still remember the Waco siege of 20 years ago with the Branch Davidians, as well as the agency's recent "Fast and Furious" blunder that let guns flow from Arizona to Mexico in an attempt to infiltrate smuggling rings.
Within the agency's offices are high-security vaults packed with guns with histories that tell many stories. They range from a pen gun, which can be converted in seconds to a single-shot weapon, to a belt-fed .50-caliber machine gun.
There are also matching gold- and silver-plated AR-15s that were taken off a suspected drug boss earlier this year.
Along the wall are dozens of handguns once owned by a Houstonian who in June was sentenced to 10 years for smuggling about 300 firearms from Houston to Colombian paramilitary groups.