He nodded. “The fact the merfolk skulls have a braincase roughly the size of a modern human’s means they too have converted to a meat-rich diet.” He scowled. “So you see, it’s my fault we’re trapped here. If I hadn’t been so eager for the reality of merfolk to conform to my paradigm of them, if I hadn’t leapt to ad hoc conclusions—”

“Stop it, Marty,” Elsa said sternly. “It was my decision to accompany you on this dive, my choice. And I probably would have made the same decision had you told me merfolk were man-eating monsters because, to be honest, I don’t think I ever bought into the idea that we would encounter one. So stop blaming yourself. It’s a waste of oxygen, something of which we have precious little. We need to figure a way out of the mess we’re in—”

“LEAVE ME ALONE. LEAVE ME ALONE. LEAVE ME ALONE.”

Elsa snapped her head toward the pool. She saw no merfolk at first. But then her light washed over two heads floating side by side. They had somehow turned off their bioluminescence, yet their mouths were once again open.

“LEAVE ME ALONE. LEAVE ME ALONE. LEAVE ME ALONE.”

One of the heads sank beneath the surface, followed by the second a moment later.

Elsa looked at Marty, bewildered. “Tell me you heard that? Tell me I didn’t imagine that?”

“They’re mimics,” he replied, grinning zealously. “Bloody hell, they’re mimics.”

Chapter 37

Chapter 37

MARTY

“Mimics?” Elsa repeated.

“Absolutely remarkable,” Marty told her, trying to absorb the revelation, while at the same time berating himself for never advancing the hypothesis himself. “But it makes perfect sense, doesn’t it?”

“Perfect sense?” She shook her head. “No. No, it doesn’t, Marty. Not to me. So please explain why merfolk speaking in my voice makes perfect sense to you.”

Mimicry, Marty knew, is widespread in nature and crucial to the survival of many species. Often it’s an antipredator adaptation in which a harmless animal shares characteristics with a dangerous or aposematic one, deterring potential predators or competitors. Viceroy butterflies evolved to look like noxious and thus unpalatable monarch butterflies. Stick insects resemble the leaves and twigs on which they live. Nonvenomous snakes adopt the colors and patterns of venomous ones.

Aggressive mimicry, on the other hand, takes a wolf-in-sheep’s-clothing approach in which the opposite occurs: a dangerous animal shares characteristics with a harmless one in order to fool unsuspecting prey. Zone-tailed hawks look a lot like turkey vultures and soar amongst groups of the scavengers to sneak up on doves and lizards and other small animals undetected. Alligator snapping turtles wiggle their worm-like tongues to lure and catch fish. The European cuckoo lays its eggs in the nests of other species of birds to deceive the host parents into incubating the similar-looking eggs and rearing cuckoo chicks alongside their own.