That brought a half-hysterical giggle from Gabriel, ending in a gurgling cough. "Don't you worry, Greg. Lots of people are going to see your tower before tonight's out. You betcha."

"Oh, yeah." He felt stupid. "Let's go." He started shrugging out of the dinner jacket, clenching his teeth as his left hand dragged through the arm, it'd swollen badly, skin stretched taut, pulling open the grazes. Trousers followed, and the discovery that buckles are tricky one-handed.

More shouting had broken out from the tower. Lots of conflicting orders interwound with Kendric's repeated urgings and Armstrong's controlled barks.

Gabriel gave him a remorseful stare before starting half-heartedly on the buttons of her blouse. Greg peeled his trousers off and helped her pull her blouse gingerly over her inflated left hand.

"Put your shoes back on," he said.

A third burst of rifle fire lashed the bricks.

They bent double, keeping the bulk of the small pyramid between themselves and the tower as they crept down to the grey slime. The stuff was semi-liquid, a thick gelatine that squelched and undulated alarmingly as Greg immersed himself. It closed around him, finding its way into every orifice. But he didn't sink. In fact the worst of it was on the surface. A sixty-centimetre stratum of water had been sandwiched between the spongy mud and lathery algae.

Gabriel groaned as she lowered herself behind him and the cold mire enveloped her.

Greg began to move, a tortuously slow sidestroke, kicking hard with his feet. Big faecal gobs of the pulpy algae clotted his right arm, splattering over his face. He had to stop every four or five strokes and wipe it off. His eyes were stung raw. Gabriel had it easier. He was path-breaking for her, clearing a ragged channel.

When they reached the second island, Greg began to worry about what kind of chase was being organised back at the tower. He looked over his shoulder and saw that someone had opened the tower's top-floor window, they were raking the torch beam over the first island and the surrounding water. The light wasn't powerful enough to reach him, but he made Gabriel keep below the wavering tops of the thin reeds as the pair of them crossed over to the island's opposite side.

Away to the right, Greg could see the bloated humps of decomposing tree trunks protruding from the algae like surfaced whales. The number, about thirty, implied some sort of park, which ruled out that direction. They needed to move fast now. Build distance before the tower blew. The park would be genuine swamp, impossible to traverse.

A hundred and fifty metres ahead were the first ranks of buildings recognisable as such; detached houses, their walls partially collapsed and roofs concave, but remaining upright. Bridging the gap was a pockmarked landscape of ash-green atolls separated by hoary stretches of slough.

"Any preference direction-wise?" Greg asked.