Officers process thousands of families crossing the border every day. Some carry memories, while others carry contraband. Because sometimes, families who travel together ... smuggle together.

While some officers wear a badge, others wear a leash. Over a thousand highly-trained K9s are on the scent, and if something's hidden, they'll find it -- because at the border, man's best friend is a smuggler's worst nightmare.

When hidden among shipments of narcotics and firearms worth billions, even the most innocent-looking contraband -- like a simple snack or sweet treat -- can be more than what it seems.

During the holidays, hundreds of thousands of people cross in and out of the US to spend time with their families, bringing with them gifts -- some naughty, some nice. But it's business as usual for the cartels; they blend in with the holiday traffic, making the season of goodwill no vacation for the officers of Customs and Border Protection.

Officers are vigilant after a recent gun show in the United States; a traveler's car is inspected when he tells officers a suspicious story about his travels; a man is caught smuggling pills and must choose between jail or giving up information.

A truck carrying household goods into Mexico is stopped for inspection; when several boxes are X-rayed, a gun and ammunition are found hidden inside a kids' toy box; a man re-entering the U.S. is stopped after checks reveal he is wanted for murder.

A driver claims he buys used cars over the border to import into the U.S., but an X-ray reveals something suspicious in his spare tire; when a traveler returning from Mexico declares snacks at Customs, a Fish and Wildlife expert is called in.

An officer suspects a car is carrying more than innocent Santeria sprays.

Agriculture specialists deal with cattle arriving without required seals.

When officers see an approaching vehicle make a sudden U-turn, they give chase and find a bag with a gun and ammunition. Tourists arrive with a large amount of Botox and dermal fillers, hinting they may be planning to perform cosmetic treatments for cash.

A man tries crossing with cosmetic injections stuffed into a sweet treat. A rookie officer follows a hunch after a Canadian narcotics smuggling trend.

Officers see a trend of narcotics being smuggled inside car dashboards.

K9s save the day, identifying gallons of paint and beer bottles filled with more than the officers bargained for; a man with a warrant for his arrest is concealing something suspicious; officers question the intentions of a chatty traveler.

A man who arrives at the border with a baby is concealing another valuable commodity; a couple who fails to declare Mexican avocados ends up causing a scene; a teenager claiming to be a U.S. citizen arrives looking to attend high school in Texas.

When a lone driver avoids answering officers' questions, an X-ray reveals dark shadows along her car's floorboard, a sign she could be smuggling narcotics; a semi-pro boxer is detained after being flagged for having a warrant for his arrest.

A cartel hitman is extradited, and 50 gallons of moonshine is intercepted.

A magician comes under scrutiny for traveling with his prop dove.

Following the work of America's Customs and Border Protection agency, whose job is to defend the border and stop terrorists, drugs and illegal weapons from entering the country.

Officers discover methamphetamine hidden inside a truck's speakers and confiscate drugs packed deep within lead boxes; a woman denies trafficking pain pills; a man is interviewed to confirm his citizenship.

Officers discover firearms that may be intended for a Mexican drug lord; a load of Fentanyl hidden in an ice cream freezer; a truck driver transporting puppies is under scrutiny; a wanted woman is detained in Brownsville.

At the Brownsville, Texas, point of entry, officers encounter drug trafficking, fraudulent documents and illegal merchandise; authorities seize $7 million worth of marijuana hidden inside a rolled carpet during a routine cargo inspection.

When a young bus driver approaches the border without any passengers in his coach, officers suspect a smuggling operation may be underway; a man attempts to drive into the U.S. with a van full of goods loaded with more than just clothing.

An illicit shipment is disguised in bags of concrete. Officers identify a criminal wanted for burglary when he attempts to cross the border. A woman is caught smuggling too many diet pills. A retired police officer almost carries a gun into Mexico.

A woman claims she drove 13 hours for a 15-minute dentist appointment, but she can't remember the name of the dentist, and has no proof of her visit. Two men returning from a night in Mexico are pulled over after officers detect a strong smell of weed.

Officers find a surprise in a car that hasn't crossed the border before.

When a drug dog alerts a vehicle full of clubbers heading to a techno bar, officers find the group has gotten creative with their illicit drugs; officers inspecting a couple's truck find bags full of rat carcasses to be used in a specialty soup. Content expanded.

As another year draws to a close, our thoughts turn to new beginnings and fresh starts. But at the border, some things never change -- certain old acquaintances aren't easily forgotten, and not all resolutions are destined to last. Here at America's front line, the one thing that's guaranteed this New Year is that the battle against smugglers never ends.

A former teacher is surprised to find she has a warrant out for her arrest.

An inspection of travelers leads to the takedown of a cartel stash house.

A truck with a compartment of drugs requires a complex code to open it.

Officers discover an illicit load within a shipment of garbage bags.

A truck stolen by the cartel in Mexico comes back to America.

An elite team prepares for the extradition of a cartel Sicario, or hit man wanted for murder in his home country; with the sale of guns and ammo strictly controlled in Mexico, cartels turn to America for the weapons to wage their wars.

A covert load of hard narcotics is found in a tractor-trailer's air tank.

A cavity search reveals a smuggler concealing pills in an unpleasant place.

An X-ray flags a dark object in the fuel tank of a a band's tour bus.

Officers struggle to open up an engine part they suspect is hiding drugs.

A man's in a bind when trying to cross with an item that fell from the sky.

A man returning from Mexico requires emergency Narcan after a suspected opioid overdose; an unlikely family is caught trying to smuggle firearms into Mexico; a woman attempting to sneak prescription meds into the U.S. is caught red-handed.

Sisters are detained when one attacks an officer after binge drinking.

A speaker cabinet is found to be carrying more than just sweet beats. A driver who took a wrong turn and ended up at the border crossing is packing more than he should be. Following a recent smuggling trend, officers carry out a special operation.

Officers find a man and his family driving a suspiciously modified truck. A young man is caught with narcotics strapped to his body. A crosser is detained for having a record of smuggling an illegal migrant across the border.

Officers uncover a lethal load. A woman and son are caught with fake visas.

When a bus is stopped for a routine search, an X-ray reveals some contents may be under pressure; a U.S. family's pet parakeet is denied entry into Mexico and without special USDA approval, it may not be allowed back into America either.

Officers catch a man trying to enter the US with a manslaughter warrant.

Officers question a man traveling with two children that aren't his; a traveler is caught smuggling cash; drugs are found concealed in a flatbed truck; a drunken man is restrained in Progreso, Mexico.

A man who claims to have been kidnapped by a cartel seeks asylum in the US.

Officers in Laredo, Texas, help a troubled 14-year-old; drugs sent through the mail are seized; a nurse in Progreso, Mexico, is caught smuggling fentanyl; a woman with children is stopped; a drunken woman bares all to officers.

A man entering the U.S. with more cash than the $10,000 limit raises eyebrows; officers find a cooler full of rat meat in the back of a traveler's vehicle, but further inspection uncovers something more surprising.

A new officer makes one of the biggest drug busts her bridge has ever seen.

A retiring officer makes a significant bust before hanging up his hat.

When a man is detained on a warrant, the mug shot confirms they have the correct man -- but his fingerprints aren't a match. A woman arrives at the border driving an oil worker's truck. Upon inspection, officers find white powder around the opening.