Rachel was still wavering and gazing nervously around when Luce took hold of her wrist. She couldn’t allow Rachel’s neuroses to ruin her chance of getting a warning to her old tribe. Luce’s nightmare of the ice blocks still had a terrible grip on her mind, and she knew it wouldn’t let go until she’d made sure the other girls were safe.

Luce kept a firm hold on Rachel’s wrist as she led her back to the tribe’s dining beach. There was Catarina’s sofa-shaped rock half-submerged as always in the lapping waves; there was the place where the black boat had bobbed with silent engines; there was the dense, rubbery seaweed matting the cliff wall, though now the leaves above the waterline were sleeved in brilliant ice. As long as the camera was still here and she could find it again . . .

Rachel kept twitching fearfully in Luce’s grip, but Luce ignored her as she dove to search among the brown leaves below the tide line. Kelp swirled into their faces as they squeezed close to the wall, Luce ransacking the leaves and fronds. After a few minutes Rachel stopped struggling. “Luce? What are you looking for?”

“A camera,” Luce told her absently. “I smashed it.”

“A camera?” Luce couldn’t have said if Rachel sounded more confused or more terrified. “Why would . . . what would . . . Luce, a camera here?”

After another minute Luce found it, its shattered lens still peeking blindly between two thick leaves, its black body wedged securely into a chink in the wall. Luce began wrenching leaves away until she’d cleared a pale circle of stone around it. “We need to make it easy to find again. So you can show everyone,” Luce explained. “But you have to tell them you’re the one who smashed it, Rachel, okay? You can’t let them know I was here.” If Anais thought the warning was coming from Luce she’d be sure to ignore it.

The two of them rose to the surface again. Cold wind licked their faces, and ice floes bucked on the lead-colored water.

“But Luce . . .” Rachel squealed. “Why would somebody put a camera here? What does it mean?”

Maybe it would have been better to find a different mermaid, Luce thought. Rachel was already close to panic. Luce hesitated for an instant and then decided that she couldn’t afford to beat around the bush. She had to make sure Rachel understood exactly how serious the situation was.

“It means the humans know about us, Rachel,” Luce said levelly. “It means they’re watching us. It’s lucky that I found this camera, but I’m sure it’s not the only one.”

Rachel opened her mouth wide as if she couldn’t decide whether to argue or scream. In the dull blue-gray light she looked sickly, almost decaying. “But then . . .” Rachel gasped and stopped abruptly.