A man was walking toward us with a crate on his shoulder. As I glanced in his direction, red lines flashed up across my vision. He kept his face half-turned away from us, and a wide-brimmed hat concealed half of the rest, but Witness – reconstructing the hidden parts by symmetry and anatomical extrapolation rules – saw enough to be convinced.

I fell silent. Kuwale waited until the man was out of earshot, then said urgently, “Who was it?”

“Don’t ask me. You wouldn’t give me any names to go with the faces – remember?” But I relented, and checked with the software. “Number seven in your list, if that means anything to you.”

“What kind of swimmer are you?”

“Very mediocre. Why?”

Kuwale turned and dived into the harbor. I crouched by the edge of the water, and waited for ver to surface.

I called out, “What are you doing, you lunatic? He’s gone.”

“Don’t follow me in yet.”

“I have no intention—”

Kuwale swam toward me. “Wait until it’s clear which one of us is doing better.” Ve held up vis right hand; I reached down and took it, and began to haul ver up; ve shook vis head impatiently. “Leave me in, unless I start to falter.” Ve trod water. “Immediate irrigation is the best way to remove some transdermal toxins – but for others, it’s the worst thing you can do: it can drive the hydrophobic spearheads into the skin much faster.” Ve submerged completely, dragging me in up to the elbow, almost dislocating my shoulder.

When ve surfaced again, I said, “What if it’s a mixture of both.”

“Then we’re fucked.”

I glanced toward the loading bay. “I could go and get help.” In spite of everything I’d just been through – no doubt thanks to a passing stranger with an aerosol – part of me still flatly refused to believe in invisible weapons . Or maybe I just imagined that some principle of double jeopardy meant that the molecular world had no more power over me, no right to a second attempt to claim me. Our presumed assailant was walking calmly off into the distance; it was impossible to feel threatened.

Kuwale watched me anxiously. “How are you feeling?”

“Fine. Except you’re breaking my arm. This is insane.” My skin began to tingle. Kuwale groaned, a worst-expectations-come-true sound. “You’re turning blue. Get in.”

My face was growing numb, my limbs felt heavy. “And drown? I don’t think so.” My speech sounded slurred; I’d lost all feeling in my tongue.

“I’ll hold you up.”

“ No. Climb out and get help.”

“You don’t have time.” Ve yelled toward the loading bay; vis cry sounded weak to me – either my hearing was fading, or ve’d inhaled enough of the toxin to affect vis voice. I tried turning my head to see if there was any response; I couldn’t.