Marvar’s worn face, the pain in his eyes, had affected him. Dyer might be impotent to protect Marvar, yet in respect of his post-it note he was not powerless. Marvar’s strange conviction that Dyer would know what to do with this had motivated every stubborn and perverse atom in Dyer’s nature to safeguard the information that Marvar had risked his life – and his family’s – to put into Dyer’s hand.

Dyer didn’t for one moment believe that he himself wasn’t in danger as well. From the instant that he lifted the Ziploc sandwich bag out of the sandpit, a persistent fear had stalked him that he never expected to feel in Oxford. The pull in his gut when walking at night, the only white face, through the favela, past the flickering gauntlet of milk-tin braziers, followed by eyes that tracked his smallest movement.

His fear was a hook that dragged him through the water. He couldn’t shake it off. Even if Updark and Katya believed that he had no further light to shed on Marvar’s breakthrough, behind them other silhouettes – malevolent, dark – flared up and vanished before he could identify them.

Who was telephoning the house? Who had left that neat scratch mark on his car like a hieroglyph? Who were the men in the Passat? Who was the man watching in the Skoda with the serrated intensity of a shoeshine boy, his lean face ghoulishy underlit from his phone?

Those who needed convincing that Marvar hadn’t given his algorithm for whatever odd reason to Dyer …

By appointing him custodian, Marvar had exposed Dyer to a hounding pack of invisible but ferocious savages who, were they ever to suspect Dyer of deceiving them, would stop at nothing to bathe their spears in his blood and in his son’s blood too.

Leandro’s lava lamp was off when Dyer went upstairs. In the dark, he peeped out between the curtains, and saw that the Skoda had not returned. He kissed his sleeping child goodnight, closed the door gently, then crossed the corridor into his bedroom and switched on the light. Marks on the furrowed sheets triggered a quick memory. But something was wrong.

Marvar’s coat is not on the bed.

He runs downstairs, three steps at a time.

On the hook in the hallway, Dyer’s leather shoulder bag. Beside the washing machine, Leandro’s blue canvas games bag from which he had retrieved his laptop less than half an hour earlier. He opens it, rummages inside. His fingers pull out Bunting’s Collected Poems and the Ziploc sandwich bag with the green folder.

The folder is empty. The float has gone under.