I’m in my usual position in the truck, folded into the passenger seat with one bare foot curled underneath me, lolling in the sunshine that glares through the dusty windshield. Sinaloa is streaming past, an endless series of desolate pueblos separated by maize plots cut out from riotous jungle. The radio is playing a bootleg tape I bought in a no-name town where we stopped for lunch. It turns out to be Los Tucanes de Tijuana, a so-called narcoband, and their album “Mis Tres Animales” — My Three Animals. Nick had to explain that’s Mexican slang for marijuana, heroin, and cocaine.

“Look! Over there! Another one!”

I follow the muscular line of his pointing arm. Tucked into the mouth of a ravine is a guardhouse and cyclone-fenced gate, the entrance to yet another drug lord’s compound. A swarthy man in a straw cowboy hat and a huge glinty beltbuckle is patrolling the fence, openly carrying an AK-47. I know it’s an AK-47 because I’ve seen several of them today, a different silhouette than the M-16s carried by Mexican soldiers and paramilitary police. I’ve also seen several of those machine guns today, at security checkpoints on the road.

“Whoever lives there, they must be bigtime,” Nick is saying. “You see how the driveway is all wide and straight and shit? That’s so it can double as a landing strip for small planes.”

“They fly drugs in and out of there?” I ask in surprise. The driveway only looks good for cars and crash-landings.

“Well, probably not drugs. Nowadays narcotraffickers mostly drop their drugs in the Sea of Cortez and retrieve them by boat. But that dude and his organization rate airplanes for travel.”

Nick has been telling me stories about Sinaloa, the brutal and bloody heartland of the Mexican drug trade. Like how Sinaloa is home to the patron saint of narcotraficantes, Jesus Malverde, a legendary Robin Hood figure who was hanged in Culiacan in 1909. And how the U.S. government actually stoked the drug trade here by subsidizing the growth of poppies back in World War II, when morphine was needed for wounded soldiers. And how the most infamous drug shootout of all time took place in Guamuchil in 1976, a high noon bloodbath that claimed the lives of drug smuggler Lamberto Quintero and his gang — but not before they’d killed half a battalion of Mexican army troops.

There are also stories that make my nerves jangle with the terror of it all. Like the long-standing practice of revenge killings — wives decapitated with machetes or chainsaws, children thrown from bridges, relatives machine-gunned. I’m also horrified by the demise of drug lord Amado Carrillo Fuentes, who died on an operating table while undergoing radical plastic surgery, his ill-fated attempt to gain a brand new face and lose 80 pounds by liposuction.

Nick doesn’t seem even slightly bothered that we’re traveling through an armed countryside of hostile camps, listening to narcocorridos that extol honor and guns and cocaine, chatting about the slaughter of innocents. He keeps turning to me with eyes like glacial lakes, relaxed behind the steering wheel, cracking jokes about this and that. Even at checkpoints, when soldiers scowl at our Iowa license plates and make him open up the back. I try not to notice the way they poke through our luggage and camping gear with M-16 barrels.

In keeping with Nick’s policy of never letting the gas tank get very empty, we stop at a Pemex station on the outskirts of a town called the 25th of January. A name full of calendrical mystery, but I’m more impressed by the Pemex. It’s a brand spanking new minimart — in jarring contrast to all the other Pemexes we’ve encountered, which were old and falling apart and had smelly gutted restrooms. This is a place I can safely pee!

He’s wandering the aisles when I emerge from the women’s bathroom. His hand flaps at the wrist, waving me over. “Hey. Tampons. You better stock up.”

I clatter across the concrete floor in my wedgie sandals, tilting my head quizzically, searching his face.

Nick misreads my look and shrugs. “I noticed you were out. They’re hard to find, you know. Most Mexican women still use pads.”

“Nah, that’s not what I was thinking.” I try to rewind the last couple months in my head. Usually I get my periods so regularly that I don’t pay much attention to their timing. But my cycle has been messed up ever since Saman took my birth control pills away. “I can’t remember if I got my period last month. Do you know if I did?”

He’s bent over a tray of wind-up toys, playing with their mechanisms. They beep and rattle and lurch for him. “What did you say?”

“Did I get my period last month?”

“Isn’t this one cute?” In his hand is a fuzzy bus shooting out sparks. “There’s enough dry tinder around to burn down the fucking country, and Pemex is selling toys that spark.”

I snatch the toy away from him and throw it back on the tray. “Did. I. Get. My. Period. Last. Month.”

“Why are you asking me?”

“Because I can’t remember!” Annoyed now, I cross my arms in front of my board-flat chest. “I think I missed it. In fact I’m pretty sure.”

“Makes sense to me. You were so dehydrated in Chirbampo you were passing out.” Nick flashes that blinding smile at me, the one that makes me puddle into affection. Then he palms my boy-butt and squeezes a cheek through my jeanshorts. “Besides, you got no junk in your trunk, girl. Your bodyfat percentage is, like, zilch. I used to have this girlfriend who ran marathons and she missed periods all the time, her bodyfat percentage got so low.”

“You mean, um…I’m blanking on the word. That medical term for when you miss periods.”

His hand falls away. “Damn. I can’t remember it either. This is going to bug me all day now.” He pinches his brow in concentration.

“Amenorrhea!” I say triumphantly.

“Yeah! That’s it. Amenorrhea.”

“Except…” A dull panic is tugging at my crooked eye. “I’ve never had that before. I always get my period.”

“You’ve never almost died of Montezuma’s Revenge before, either.” Nick nods at the shelf, where the reassuring soft blues and pinks of tampon boxes are stacked between cold remedies and toothpaste. “Get what you need and let’s vamanos.”

I fill my arms with Tampax Satin Teens, if I’m translating the label correctly, and clatter after Nick. He’s cherrypicking snacks off the shelves he passes, jerky and churritos and sunflower seeds, and predicting that we won’t stop again until Mazatlan, a tourist paradise that seems so misplaced amidst Sinaloa’s narcotraficantes and machine guns and drugs.