Early afternoon, after we crossed a stream by way of a massive downed tree, Omar stopped short and raised a hand for silence. He pointed at the ground; to my eyes only the usual snarl of vines, tangled roots, and leaf litter. The air shuddered with the call of parakeets.

He picked up a sapling that had been bent into an L shape and laid across the path. “They know we’re here.”

“It’s just a—”

Again he silenced me. Why that branch looked special to him, among all the other bent branches, remains a mystery to me. I tried to read his face; I saw no fear, but knew how well he masked his own trepidation, knowing if I saw a shred of it, I would be too terrified to go on. We walked another couple of hours through claustrophobic tunnels of towering saw grass and hanging vines, through the constant twilight.

At the foot of a rubber tree, he turned and held his finger to his lips—even though I hadn’t uttered a word for hours—held his other hand out to stop me, then pointed up. Just above his head, a tapir skull—two feet long, black with age, molars yellow—sat wedged in the crotch of a tree. A column of black ants trekked along its cranium, vanishing in the hollow of a gaping eye.

“What does it mean?” I whispered.

“It’s a sign. It means go away.”

“They’re going to kill us, aren’t they?”

“They would have done it by now.”

He slapped a hand over my mouth just as a cry escaped my throat. My cheeks burned under his cool, dry fingers. Even now his face read blank to me; could it be he felt this insane plan might work? I had no such confidence. I blinked tears out of my eyes, dropped my head back in his arms, sent prayers to the impenetrable canopy as he slowly, carefully took his hand away. A leaf dripped its sweat onto my forehead.

“We have to go back, Omar, please, what good is it—”

“Come on.” He disappeared into a thicket of tree ferns dozens of feet tall. I followed the hard whack of his machete as he slashed our way to a small clearing, where a stream burbled among the immense roots of a ficus tree. White, disc-like fungus, like plates, clutched at various intervals at the base and lower branches. On one of them something steamed with a corporal energy. A pile of entrails had been placed neatly in its center.

“Another sign?”

He motioned for me to be quiet. The shrieks of spider monkeys shattered the silence. I looked up. The trees hung with a terrible stillness.

“Where are the monkeys?” I whispered.

“Those aren’t monkeys.”

The calls grew louder, closer. Directly overhead, all around us. A shrill note of fear in them now. I turned in a circle, peering up, hugging my filthy burlap dress to my ravaged skin. Nothing but the canopy, unmoving.

“The Tatinga are mimicking the monkeys. They’re hunting them. Making the calls of distressed infants. Come on, we can’t stop here.”