Up ahead of them the Cherwell joined the fast-running Thames just upstream from Follies Island.

‘For Christ’s sake, Oliver. Where are you going?’

Tom was almost on his feet but the boat rocked violently and he sank back again. The banks slid away on either side of them. Rushed on by the water as the tributary ran into the river, they were out in the mainstream.

‘Tired of pissing about up there. Let’s do some real boating.’

Oliver’s face was stretched into a wide, exhilarated smile. They couldn’t see it, but his eyes had come alive with reckless light.

‘The bank. Steer into the bank,’ Tom shouted at him.

Ahead Helen glimpsed the square outline of Follies House sitting on its little island, the three arches of the bridge carrying their ribbon of orange light across the river, and the curl of white water licking around the piers.

Tom’s arms were steadying her.

‘Keep still,’ he hissed. ‘Lie flat. Calm water past the bridge.’

The white water hurtled towards them, and the bridge.

‘Oliver.’

It towered unbelievably high above them.

‘Oliver,’ Tom was yelling. ‘Steer left.’

The central pier was coming straight at them. The noise of the water was deafening. The prow swung sharply and missed the mossed stone by inches. Helen saw water sliding over the varnished wood and lapping down towards her. The punt swung giddily under the arch. Almost before it happened she heard the splintering crash as the stern smashed against the stone. There was a crack and a sound that might almost have been a cry.

The rushing water swallowed it up. The stern suddenly bobbed upwards.

Helen looked back. No-one.

‘Oliver,’ she screamed.

He was gone.

FOURTEEN

Desperately Helen struggled to climb backwards.

Tom’s hand held on to her with a grip like iron as icy water foamed over the sides of the boat and soaked them. The force of the smash sent the punt juddering sideways. Within a second they rammed into the bank beyond the bridge. Instantly Tom flung himself forward and caught at the rough grass.

‘Climb out,’ he shouted. ‘Move.’

Helen felt a useless scream rising in her throat as she scrambled over him to the towpath. As soon as he saw her safe, Tom pushed the punt away and struck out for the bridge.

Beneath it the water was black and white, empty.

She heard another splash and saw a head bobbing in the fast water, swimming like a dog. Blond hair plastered to the skull. Unmistakably shaped.

Relief surged inside her.

‘Tom,’ she screamed. ‘Over there. Swimming.’

She ran along the path and into the booming space under the bridge. Gravel bit into her feet through her thin shoes and her dress clung around her ankles in hobbling folds. The swimmer was circling, dipping constantly under the threatening white foam.

What’s the matter with him? Why doesn’t he make for the bank?