‘I’m an engineer, Ispettore,’ he finally said. ‘So it interests me professionally. In terms of cycles of consumption and production.’

‘I figured you’d studied,’ Vianello said. ‘But I didn’t know how to ask you.’ After waiting a moment to see how Bambola accepted this last, he asked, ‘What sort of engineer?’

‘Hydraulic. Water purification plants. Things like that.’

‘I see.’ Vianello pulled some change from his pocket, sorted through it, and left the right amount on the bar.

‘If you speak to Sergio,’ Brunetti said as he moved towards the door, ‘please say hello and tell him to get better.’

‘I will, Commissario,’ Bambola said and turned away towards the two men at the end of the bar. Brunetti had expected Vianello to return to the subject of his aunt, but the impulse, it seemed, had been left in the Questura and Brunetti, having no particular desire to continue that conversation, did not pursue it.

Outside, both men paused involuntarily under the whip of the sun. The Questura was less than two minutes’ walk, but in the heat that appeared to have increased while they were inside, it might have been half a city away. The sun blasted down on the pavement along the canal. Tourists sat under the umbrellas in front of the trattoria on the other side of the bridge. Brunetti studied them for a moment, seeking some sign of motion. Could it be that the heat had dried them out, and they were no more than empty shells, like locusts? But then a waiter took a tall glass of some dark liquid to one of the tables, and the guest moved his head slowly to watch his arrival.

They set off. Bodies of water, Brunetti knew, were meant to cool the places where they were found, but the flat, dark green surface of the canal seemed only to reflect and redouble the light and heat. Instead of relief, it provided humidity. They trudged on.