Jane listened to the crew’s diagnosis and projection. With only battery power, there would be no radio altimeter for precise height indication. Not even any landing lights. The captain wouldn’t be able to lower her flaps, so the ditching would be fast — faster than the stall speed of a hundred and seventy knots — the engines would surely break off on impact; the wings and structure would be damaged…

The cloud cleared; low sunlight poked into the cabin, briefly dazzling Jane. The play of electrical light over the windscreen dissipated.

The flight engineer cried out. “Number four has restarted!”

Now Jane felt the roar of the engine; she could see the engine gauges rising, the power settling. Gingerly the captain advanced the thrust lever, and the engine was running at normal power.

They had ducked under the ash cloud, she realized; that was what had enabled the engines to start.

“Here comes number two,” the captain said.

“Prestwick,” the SFO said, “we seem to be back in business. We have diverted back to Prestwick and will land in fifteen minutes.”

“Number one. Number three.”

The captain pulled the plane into a shallow climb. Immediately the cabin was swamped by the dark, smoky cloud once more, St Elmo’s Fire dancing on the windscreen.

“Good God,” the captain said. “Bugger this for a game of soldiers.”

She dropped the nose, and the plane dipped beneath the volcanic cloud and into the light once more.

An engine surged violently, recovered and surged again. The bangs were audible on the flight deck, and the aircraft shook.

“We’re going to have to nurse this poor old girl home,” the captain said. “Shut down drill, number two engine.”

Jane peered through the windscreen. There seemed to be mist lingering there, or perhaps spilled oil, but the busy wipers were having no effect. It was sandblasting, she realized, scarring by particles of volcanic ash.

Even inside the cabin there was black dust on every surface. Jane picked it up between thumb and forefinger. It was gritty, with a sulphurous smell.

When she looked out, through the murky windows, she could see a new ash cloud, miles wide, still higher, black as coal, reaching into the air from some new geological horror.

If that cloud had been a little lower, if the base of the ash had dropped to ground level, the plane wouldn’t have got out.

Cautiously, leaning to see through the remaining clear patches of windscreen, the captain nursed her craft to the ground.

…And now, three seconds in, the rumbling got louder, and the cabin started to shake. Henry knew he must already be off the ground, but the booster was poised there, burning up its fuel just to raise its mass through these first few yards.

So here he was, locked into a cabin on top of a Soviet-era ICBM, which was balanced on the rocket flames jetting from its tail.