A rolling thunderboom reached us from the north now, muffled and too deep, so I felt the vibration in my bones more than I heard it. That made it real. Sardinia is small; it was less than ten kilometers northwest from the Forum to the north coast of the island, then another twenty kilometers of sea to where New Atlantis nestled on the seafloor between the encircling coasts of Sardinia and Corsica, like a chick cupped by kindly hands. I had visited Utopia’s underwater city myself, seen the crystal bubble-domes framed by struts whose surfaces teemed with barnacles and weedy life. I had schooled there with wrasse and damselfish along arched shopping galleries, swim-raced friends from spire to spire, played fetch with octopus, and watched patrolling hippocampus herd young sharks away to safer waters. I spent a week there once, long enough to half forget the pack that breathed for me, to stop craving the air-filled sections, and to almost shake the terror of the warning videos about how, if I returned to the surface world too fast, my blood would bubble and bring pain, paralysis, and death. Someone had attacked Atlantis. The blast had been big, big enough to feel thirty kilometers away, but how big? Small enough to crush some structures, flood the airy sections, but leave the swimmers safe? Big enough to end all life in the ocean city in an instant? Or was it cruelly in between, so helpless thousands were now being dragged up by the currents toward the sunny surface, screaming like Icarus?

Now I realized Mycroft wasn’t next to me. I panicked, spun, searched, saw. Mycroft always said that they could fly. This run was flight, a run across the crowd, leaping from shoulder to shoulder like a mantis, taking off again when each startled human foothold toppled. True it was Earth and leg muscle that lifted Mycroft then, not air and wing, but what is flight if not soaring above those who let gravity confine them? Mycroft leapt, and seized the leg of a whirring robot with both arms, and, after a moment’s indecision, the Delian rider helped Mycroft swing up to ride behind them. I heard Huxley beside me mutter as they mounted their own black lion to join the exodus. A whole layer of life lifted away from the Forum, taking with it color, texture, animal breath, and a hundred brilliant suns, leaving the Forum gray.