‘Dr Greystone?’ Raz sounded blank. ‘I have never met this Dr Greystone.’

Casey stared out of the windows. There was water everywhere in this city: in puddles, in canals, in pools under motorway bridges. A dilapidated lorry hurtled by, piled high with sacks, a small boy clinging to the very top. The lorry’s driver was old, with a beard that would have been white, had it not been dyed the startling henna orange. The small boy waved at her.

‘We were thinking,’ Casey said brightly, waving back, ‘that as we have a few days here, we might head down to Cox’s Bazar.’

Chittagong, Bangladesh’s industrial powerhouse, was 150 miles south-west of the capital Dhaka, further down the Bay of Bengal. Cox’s Bazar was beyond Chittagong, another four hours along the coast.

Not far north of the Burmese border, Cox’s Bazar was the closest thing to a tourist resort in Bangladesh. Named after Captain Cox, hero of the East India Company, the ramshackle town sprawls along one of the longest beaches in the world, almost a hundred miles of sand.

The Bangladeshis thronged to Cox’s Bazar at this time of the year, the women swimming fully dressed in the sea, the hawkers hustling to and fro. Photo? Sunhat? Photo?

‘Cox’s Bazar is a nice place to go,’ said Raz cautiously. ‘Certainly, for a few days, you might enjoy yourselves there.’

The Rohingya refugee camps were an hour’s drive further on from Cox’s Bazar, spreading over hundreds of acres just to the north of the Myanmar border. Cox’s Bazar itself had been flooded with aid workers, who had been commuting down to the camps for years now. The big humanitarian agencies blockbooked the holiday hotels for months at a time, almost smothering the tourism.

‘Those women will be somewhere in the area around Chittagong and Cox’s Bazar,’ Casey had insisted to Miranda, back in the office. ‘The man Hessa spoke to had a Chittagong accent, according to her mother.’

‘Maybe,’ Miranda had shrugged. ‘You can’t be sure. They could be anywhere. In the outskirts of Dhaka, wherever. And just because he has a Chittagong accent, it doesn’t mean he still lives there.’

Snug in the black Land Cruiser, Casey cracked open a bottle of ice-cold water, and leaned her head back against the plush headrest. ‘Would you arrange a car for us down to Cox’s Bazar tomorrow?’ Casey put on Emily’s confidence like a coat. ‘It would be so helpful.’

Raz would expect them to be driven. In Dhaka, the Bengali elite were driven everywhere by a chauffeur. With at least one bodyguard, and the horn blaring. Quite often they travelled in convoys, in a cloud of weed and coke.

‘If you want to go to Cox’s Bazar,’ said Raz, ‘it would be much easier for you to fly. The highways, they can be very dangerous.’