After so long thinking about it all I felt like I had a hangover.

I was on my way to deliver a USB key to a client when Matthew called me. That was quick, but I guess he is a mathematician.

We met in a dodgy alley – it was perfect: tucked between two cracked concrete buildings in an industrial area strewn with litter and stinking of decay. He was still in his lab coat, holding a cigarette in his shaky hand. His eyes were still haunted, but now they seemed to flash with a fury. On seeing me, he jumped out of his skin, dropping his bag; all his stuff fell out.

He started talking, practically in falsetto: "I'm getting on board. And I've got a five-star gift for you: I've got a cheap way to make prime numbers! But first things first: we split 50–50, because, frankly, you need me! And if you try even the slightest threat like 'I'll break your fingers,' or you look at me funny like you're about to get rough, then I'll quit and you'll let me quit. Clear?"

I put on a solemn face, trying to feign an air of respect, even though I genuinely didn't respect him at all. I told myself I'd break his fingers or worse if I felt like doing that – because if I felt like doing that then there would be a good reason. I was aware that right now he was betraying his boss, and that he could easily betray me the next day.

I bowed my head and shook his hand. "So, now we are partners," I replied. From then on I was in business.