The heat in the rear of the lorry is unbearable. The midday, Mexican sun cooks the corrugated metal walls, turning the inside into an oven. Only a trough of foul, greenish water is there to provide relief, shared by all the other animals, though even as parched as you are, you've not stooped to drink from it.

The suspension has rusted out. Every time the truck hits a bump in the pitted road, it lurches, and the donkeys on either side sway against you, pressing your mutilated body between their hot, sweaty flesh. You live in mortal fear every time they crush against your bloated flesh, knowing that a single pop from the overfilled plastic sacks inside would be a death sentence.

"¡I can't breathe! ¡Pull over!" you call out to the driver. "¡I need water, air, anything!"

"¡Eres un burro! ¡Shut your mouth back there!" the driver barks. "We're almost at the border. Are you trying to get both of us killed? The Americans will shoot us if they hear one word from your mouth." He twists around to look back at you. "And what the hell are you standing for?! Are you stupid? They have cameras everywhere. Drones." He gestures skyward. "Get down on your hooves now."

"I can't. There's no air back here. These animals will crush me."

The man swears under his breath and rummages in the glove compartment. He stretches an arm over the back of the seat, cocking a revolver before your eyes. "If you don't get down on the ground like a donkey now, I'll shoot you myself, and that would be doing you a favor if you knew what the Americans would do if they find you. They have a special farm where they keep cockless mules like you. There will be no trial. You will be branded, fitted with a nose ring, and dragged away to be used as a mare, fucked by fat donkey cock for the rest of your days. Is that what you want?"

The fear of that is enough to bring you down onto all fours. The modified joints of your pelvis slip comfortably into the quadrupedal stance, your skeletal structure settling into the perfect imitation of a donkey. The hooves that are now your hands clunk against the straw-strewn floorboards. Behind, your meaty, naked hindquarters are thrust high, horribly exposed; your vulnerable equine equipment is exposed with each swish of the grafted tail.

Back in Colombia, you'd been a farmer, a big man - only the largest of men could be converted into the smallest of mares. You had been desperate for money. When you approached the cartel, you'd envisioned the life of smuggling much like Miami Vice. Glamour, sex, huge shoulder pads, sailing across the border in a helicopter with half a tonne of cocaine. Not this.

You had been skinned. Their henchmen had been startling adept at the practice. After, they'd grafted you inside the freshly flayed flesh of a female donkey. Rousing from the anesthesia had been like a waking nightmare, clawing at your face fused inside the elongated snout of an animal with your blunt hooves. But the cruel reality of their demands had forced you to focus. You were their drug mule now. You would do everything they asked to pay them back for their 'generous' surgery. If you ever wanted to be a human again, you would have to pay them back. And if you refused, there was no end to the punishments that could mete out on an animal like yourself. They took great joy in describing them, even showed you some of the captive 'lifestock' they kept on the compound - men who had failed to meet their repayments.

The truck lurches again as it pulls into the border checkpoint. The plastic implants peppered throughout your body, filled with gallons of cocaine dissolved in solution, slosh, and jiggle. You hear American voices shouting for the van to pull over for inspection, and the tailgate behind you being opened. You bite your tongue, heart pounding in your ears in terror, and press closer to the donkey beside you to hide. You feel the border agent's hands on your rear, as he begins to inspect you.