“I’ve been inside your firewall for exactly forty-two seconds, and I have to say, your encryption protocols are as outdated as a dial-up modem. Are you even trying, or is London making you soft?”

Sandro Lancaster didn’t move. He sat in his dimly lit flat in Shoreditch, the blue light from three curved monitors reflecting off his glasses. Outside, the London rain was a steady, rhythmic thrum against the glass—a sound he had grown to prefer over the stifling silence of the Aldridge mansion. He took a slow sip of his black coffee, his eyes tracking the scrolling green lines of code on his center screen.

The intruder wasn’t just...