“Sorry, Harper.” Gemma turned around so she could look at Harper and walked backward out of the cabin with Penn. “Take care of Alex for me, okay?”

Thea and Lexi sprinted ahead, running down the trail.

Harper stepped forward, saying her sister’s name, but Gemma just shook her head. She turned around, and she and Penn raced down the trail. Harper chased after them, but Gemma was too fast, much faster than she’d ever been before.

“Harper!” Daniel yelled, and he got up and ran after her, meaning to stop her from doing anything stupid.

By the time Harper reached the dock, Penn and Gemma were already at the end of it. Gemma glanced back, then dove into the bay.

The sun had begun to rise, bathing the water in pale pink light, and Harper could see Thea and Lexi swimming away. They’d already transformed, and their mermaid tails splashed out of the water before they dove down.

Just as Harper made it to the end of the dock, she felt Daniel’s arms around her, preventing her from leaping into the water after her sister. Her arms were outstretched in front of her, as if she thought she could grasp Gemma with them.

“Gemma!” Harper shouted and tried to push Daniel off her, but he refused to let go.

Gemma surfaced just once, but she never looked back toward the dock. Harper just saw Gemma’s head, and then the iridescent scales of her tail shimmering in the sunlight before she submerged.

“Harper, stop.” Daniel’s voice was firm in her ear. “She’s not coming back, and where she’s going you can’t go after her.”

“Why not?” Harper demanded, but she stopped struggling. “Why can’t I go after her?”

“Because you can’t breathe underwater, and you don’t know what you’re fighting against.”

The fight went out of her, and she went lax in his arms. Daniel lowered her down to the dock, and she knelt on the end of it, still staring out at the ocean. He knelt behind her, his arms still around her.

“What the hell were those things?” Harper asked.

“I have no idea. I’ve never seen anything like that.”

“So I’m just supposed to let her go off with them, and do nothing?” Harper turned to look back at him, her face right next to his.

“No, you won’t do nothing.” Daniel shook his head. “We’ll find out what those things are, figure out how to stop them, and then we’ll go get your sister back.”

“But she’s with them now. What if they hurt her? What’s to stop them from killing her?”

“Harper,” Daniel said as gently as he could. “You saw her swim off with them. She looked like a mermaid.” He paused. “She’s one of them.”

“No, she’s not, Daniel. She’d never hurt anybody. She’s not like them!”