Braced against the motion and took a step. I would be killed thirty feet away, no question. I couldn’t get any deader by being any closer. I passed the Hispanic woman on my left. Passed the guy in the NBA shirt on my right. Passed the West African woman on my left. Her eyes were still closed. I handed myself from one grab bar to the next, left and right, swaying. Passenger number four stared at me all the way, frightened, panting, muttering. Her hands stayed in her bag.

I stopped six feet from her.

I said, ‘I really want to be wrong about this.’

She didn’t reply. Her lips moved. Her hands moved under the thick black canvas. The large object in her bag shifted slightly.

I said, ‘I need to see your hands.’

She didn’t reply.

‘I’m a cop,’ I lied. ‘I can help you.’

She didn’t reply.

I said, ‘We can talk.’

She didn’t reply.

I let go of the grab bars and dropped my hands to my sides. It made me smaller. Less threatening. Just a guy. I stood as still as the moving train would let me. I did nothing. I had no option. She would need a split second. I would need more than that. Except that there was absolutely nothing I could do. I could have grabbed her bag and tried to tear it away from her. But it was looped around her body and its strap was a wide band of tightly woven cotton. The same knit as a fire hose. It was pre-washed and pre-aged and pre-distressed like new stuff is now but it would still be very strong. I would have ended up jerking her up off her seat and dumping her down on the floor.

Except that I wouldn’t have gotten anywhere near her. She would have hit the button before my hand was halfway there.

I could have tried to jerk the bag upward and swipe behind it with my other hand to rip the detonator cord out of its terminals. Except that for the sake of her easy movement there would be enough spare length in the cord that I would have needed to haul it through a giant two-foot arc before I met any resistance. By which time she would have hit the button, if only in involuntary shock.