Walking through the airport made me realise what a state Amelia and I were in; I was already filthy when we left the mine and hadn’t changed my clothes since then. Joseph, in his ironed jeans and bright white shirt, did a double-take when he saw us.

‘Long story,’ I said.

‘No excuse!’ he replied, leading us to the airport toilet block. ‘Nobody flies with me so … not clean!’

My spare T-shirt wasn’t much better than the one I was wearing, but I stripped to the waist at the sink and got the worst off myself at least. Amelia did better than me in the ladies. She emerged looking fresh-faced, tanned – she’d caught the sun – and her wet ponytail swung cheerfully from side to side as we made our way out to Joseph’s plane.

This time our arrival back in Kinshasa really did coincide with a proper storm. The sky filled with black clouds while we were still some way from the airport, a mean weather front closing in. Joseph pushed his aviators up onto his forehead and dropped the plane a thousand metres so fast my stomach jumped. ‘We can beat it,’ he said with a sideways smile, and began arguing with air traffic control. Raindrops big as marbles whacked against the cockpit glass loud enough to be audible over the propellers. The storm front was like a lid closing on the runway. Joseph murmured, ‘No problem, no problem,’ and smiled at us as we descended further, but there were pinpricks of sweat along his hairline. We flew the last kilometre at an altitude of about two hundred metres, crabbing sideways against a horrible crosswind. Being able to see what was going on made the whole thing doubly exciting. I could tell Amelia was worried though; she was gripping the sides of her seat.

‘Nearly there,’ I reassured her, with the runway a rain-warped streak of grey ahead. Joseph kicked the plane straight at the last second, and the wheels kissed the tarmac amazingly gently.

‘Easy, as I said,’ said Joseph casually, but his relief as we taxied off the apron was obvious.

Once Joseph had fast-tracked us through the airport to the taxi rank, Amelia dug out her phone again. Mine was dead, but she’d thought to keep hers switched off until we needed it. Now she turned it on and showed me the messages that had landed more or less as we did. Once again hope fluttered in my chest: might Mum or Dad have made contact? No, but Caleb had.

His message read: ‘Heads up – my dad’s on his way. Cx’

Despite everything, I couldn’t help flinching at that ‘Cx’. The fact that Caleb hadn’t said what had happened when Langdon came round worried me.

‘Message him back,’ I told Amelia. ‘Ask him how it went with his dad when he woke up. Also, ask for Langdon’s Kinshasa addresses – both home and work.’

‘Yessir,’ said Amelia.