Her breath came quicker. Beaten, she rubbed at her face. Her eyelids were heavy, as though she’d been awake for days, and she moved over to a chair and sank into it. She noticed she hadn’t closed the sliding doors fully, and the curtain flapped in the breeze, the chill coming into the room making her shiver.

Should close the door, she thought, but suddenly it was too much effort to lean forward and slide it completely shut. With the wind howling outside, she leaned her head back and closed her eyes. Confusion overcame her, just moments before sleep.

For dinner, Anna dressed in a simple black jumpsuit, a thin gold chain around her neck and her make-up natural. She grabbed her black clutch, put on her tallest stilettos and let herself quietly out of the suite.

The corridor was empty and silent, and the ship’s engine hummed a gentle tune beneath her feet. She smiled; they were on the move, and tonight, after the meal, they would be far enough out in the open ocean that she could dispose of Mark. But first, she had other plans to attend to.

Outside Tommy and Paula’s suite she stopped and pulled Mark’s master key from her purse. He had been more than happy to tell her all about the workings of the ship, and the most surprising one had been the keys. In the event of an emergency – striking another boat, or terrorism, or something else that threatened life – the passengers were to return to their suites or cabins. At the captain’s discretion, all the doors would be locked from the outside. Controversial, Mark had said, but sometimes necessary. Also, not something that the shipping line advertised.

And it had worked, Anna saw now. Just one turn of the key when she had left the Expedition Suite earlier and the red light was still glowing on the door handle button. She inserted the master key now, and with the softest of clicks the door opened. With a palm flat on the door, she pushed it open far enough to slip inside. The room was in darkness now, but the outside balcony lamp cast a strip of light that cut through the centre of the room. In the chair nearest the door sat Paula, her head back, her breathing deep, heavy and even.

Anna smiled to herself and backed out into the hallway, pulling the door to but not closing it fully.

The restaurant was heaving, the passengers seemingly revived and in high spirits from their day on land. Anna made her way to the far side, near the floor-to-ceiling windows and Tommy’s usual table.

He saw her approach and stood up, waving to her with a yell. ‘Anna!’ he called. ‘Over here.’