Still, he doesn’t blame Zoe for his downfall, even though she engineered what had happened, offering to escort him home, allowing him into her room. And yes, he slipped her something in her coffee but he didn’t understand what he was doing, not really. The phial had been given to him by one of the third-year students at the Maths Society party who’d seen how he followed Zoe with his eyes. The student sidled up to him, slid the phial into his pocket, and laughing, said, ‘That one is way above your pay grade, mate. You want some action you’ll need to slip this in her drink.’ He’d winked and put a finger to his lips. Later that evening Cullen noticed him standing with another student, looking at him and laughing. They considered him comical, his love for Zoe a puppyish crush. It made him burn inside, as if someone had made him swallow bleach. Well, he thought, I’ll show them. And what harm had he done really? Zoe couldn’t even recall what had happened. It was Honor who had stirred up the trouble. The jealous bitch. He’d seen the way she looked at Zoe. Why persecute him, a fifteen-year-old boy, who barely knew what sex was, and had never been told that you had to ask someone for it and doesn’t believe that even now. Women are vixens. They never think twice about taking what they want when they want it but bleat like sick lambs as soon as the tables are turned. Zoe caused him pain but it was Honor who ruined him, who turned up at his door and bothered his mother and harangued St Olaf’s until the university had no choice but to ask him to leave. He had been ruined by a single malevolent spirit.

It’s payback time. Revenge is the only way to close the circle, to leave the world a tidier, more orderly place. To solve the equation of his own misery. It would be too easy to kill Honor. This way is better, more creative. Solving an equation is, after all, as much a demonstration of the beauty of the process as it is about finding the right answer. There would be nothing to stop him sneaking onto the boat and cutting Nevis’s throat. But where would be the skill or the beauty in that? Revenge, he realises, has its own logic. It is very much like mathematics in that regard. No wonder that he finds both magnetic.