In the next moment, Yegor jerked again, and his huge body came up to the thighs, and then he slid forward over the side of the hull, to splash in the water. The large Russian bobbed for a moment, and then sank.

“Shit.” Jack dived in.

“Jack…” Cate dropped her flashlight and followed him in, stretching out far as she dived. She swam to where Jack had followed Yegor down. The water tasted of salt and machine oil where the submersible had been. It was also the warmest water Cate had ever felt in her life. She had swum down, perhaps twenty feet, until the pressure on her ears started to become painful. She waved her arms around, but there was nothing – it was an impossible task, as the water was blacker than hell.

A light current brushed her face, and she immediately jerked back, remembering the things they had seen, and realizing she might not be alone in the water. She pulled back, and then stroked hard for the surface.

Cate breached and sucked in a huge breath, a light’s glare immediately in her eyes.

“Cate…” Greg was holding his flashlight up at her, the beam only just illuminating the water around her. She felt something strike her legs and she screamed. Jack burst from the depth beside her.

He spluttered for a moment, and sucked in more air, once, twice, and Cate realized he was getting ready to dive again. She grabbed him.

“Forget it, he’s gone.”

Jack face was screwed in torment. “Goddamn it.”

She pushed him towards the ledge. “We’ve got to get out.”

They swam fast, and clambered up on the slick rocks, Greg hauling them up like fresh caught fish onto a boat’s deck.

She and Jack knelt, coughing, and Greg helped Abby sit up when she groaned, still lifting from her stupor. They stared, still in shock and confusion – the submersible was now fifty feet from the ledge, and the hatch on top closed with a deep and final clang. The Prusalka then began to ease around to face them.

Cate could just make out the red glow of the interior, and Dmitry, the sole pilot at the controls. He grinned, and lifted a single hand, the fingers just curling in a comical wave of goodbye. Then the craft slowly began to submerge.

“No!” Jack yelled, the shout bouncing back at them inside the huge cavern.

Behind them Greg hugged Abby, who was sobbing softly.

“I don’t understand – where’s he going?” Greg brushed the slick hair back off her face. “Is he going for help? Was there a fight… with Yegor?”

Jack exhaled long and slow. “I don’t think so.”

“Is he coming back?” Greg blinked several times. “Maybe he saw something, and needed to keep the Prusalka safe.”

Jack scoffed. “Yeah, and Yegor just decided to go for a swim… after he shot himself.”

Greg shook his head. “We don’t know—”