‘Ben here, in deepest Brazil. Searching for the lost city of gold!’

Ben stood on the deck, filming the jade-green water across to the riverbank. He still couldn’t believe he was really here. The Amazon! A few weeks into the research expedition with his dad. It was the trip of a lifetime.

Sunlight glinted off the dense line of trees. Ben zoomed out; he was using the video camera on his phone. ‘Here’s our fine vessel. A wooden cruiser. Only fifteen metres long. Bit on the old side. Been doing a bit of trading on the way. Got some cargo loaded last night – captain won’t tell us what!’

Light sparked off the water. A shoal of silver-backed fish broke the surface, then slipped back into the depths.

‘Poisonous snakes in there.’ Rafael was by Ben’s shoulder. ‘Electric eels and piranhas, too,’ he added nervously, adjusting the bulging fabric of his life jacket. ‘I read them fishes can eat a whole man in two minutes – right down to the bones!’

‘Don’t forget them crocodiles,’ teased Ben, turning the camera on his friend. ‘Here’s Rafael. Give us a wave, Raffie! Portuguese explorer extraordinaire. Expedition expert on all things that can kill you out here. His dad is paying for the trip, so got to treat him right … Leech on your neck!’

Rafael gave a gasp and swatted at his throat.

The video shot shook with laughing. ‘Oh, sorry,’ said Ben. ‘It’s just a leaf.’ He gave Rafael a friendly punch on the arm.

‘That’s not funny,’ Rafael puffed. He put a hand up to the lens. ‘Stop filming me. Now! Who’s going to watch that, anyway?’

Ben shrugged. ‘Not been able to get a signal since we got so remote, but 900 hits and counting last time I looked!’

‘Hmph!’ said Rafael, but he looked impressed as he bustled off, scribbling in his notebook.

Ben zoomed in on a man wearing tatty shorts and a T-shirt. ‘Here’s the good doctor of archaeology himself! Checking the GPS. Could do with a shave. Hi, Dad!’

Dad gave a small salute. ‘Greetings, my one and only son!’

Ben panned to the wheelhouse – but the captain put up a hand and waved him away with a frown. ‘There’s our Brazilian skipper – laughing and joking as usual.’

There was the smell of smoke and, as they rounded a bend in the river, a cluster of thatched huts came into view along the bank.

‘Espírito,’ called the captain gruffly from the wheelhouse. ‘Last village for fifty kilometres.’

‘Getting some good shots?’ Dad clamped a hand on Ben’s arm and gave it a squeeze. ‘This is the life, eh? On the trail of the real El Dorado.’

Ben stopped filming and grinned. ‘Think we’ll really find it?’

‘We’re on to something, son.’ Ben felt his heart thud, catching Dad’s excitement. ‘What with the aerial photos, and the new lead I got from that museum in Rio de Janeiro …’ Dad’s eyes glittered. ‘I think this could be it!’

Ben smiled. He’d not seen his dad this happy in ages. ‘Hey, maybe we’ll find the tons of gold Rafael’s dad is after! Beat everyone else to it!’

‘El Dorado!’ Dad breathed. ‘But I’m not here for the gold, Ben.’

‘OK, right!’

‘No, seriously,’ said Dad. ‘It’s knowledge I want to find. To understand how the local people lived. Get the place protected. Preserved for future generations.’

Ben nodded. He looked over at Rafael, still scribbling in his notebook under the awning. ‘But when are you going to tell Raffie’s banker dad we’re totally off his route?’

‘Yeah.’ Dad looked uncomfortable. ‘We’re due an update call any time from our Senhor Santa Lucia.’

The boat gave a lurch, and there was a wave of curses from the wheelhouse.

‘O … K,’ said Dad. ‘Looks like we’re stuck on another sandbar.’

There was a grating roar as the captain revved the engine backwards, forwards, churning up mud and silt as he tried to get the boat free.

‘Do the emergency canoes have enough supplies in them?’ called Rafael worriedly, fiddling with the straps of his life jacket.

‘Don’t worry, Raffie,’ Dad reassured him. ‘That’s all taken care of.’

There were shouts, and a group of small children ran along the riverbank ahead, laughing and waving. A fallen tree jutted out of the water; Ben saw a girl balance expertly on a branch. She was about his age, with black hair to her shoulders. She had a band of red paint across her forehead, and swirling black lines along one side of her face. The girl ran effortlessly along the branch and dived into the water.

Next moment she was on the surface again, swimming to the boat with gliding strokes. She shouted something to the other children, and there was a flurry of movement as they jumped into the water and swam behind her in a giggling shoal.

Ben got filming again. ‘Captain’s feeble attempts to free the boat failed. Locals coming to help.’

‘But what about piranhas?’ fretted Rafael.

Ben saw his dad watching in amusement.

Dozens of small hands pushed at the side of the boat, helping the growling engine.

There was an explosive cheer as the hull came free, and as the boat gathered speed the kids came in pursuit.

‘Thank you! Thank you!’ called Ben, waving.

‘You are welcome!’ the girl called back in English. ‘But keep to the left!’ she shouted as she fell further behind. ‘The right branch leads to rapids!’ Ben could hardly hear her now as the river curved again. ‘Drowned ghosts!’

He lost sight of her.

Rafael unrolled a map and started peering at it. ‘What did she mean about rapids?’ His voice was twangy with stress. ‘There shouldn’t be rapids on our route!’

Ben and his dad exchanged looks. ‘Just a little change of plan, Rafael,’ said Dad soothingly. ‘I’m going to tell your dad all about it when we next talk.’

‘But white water is totally lethal!’ cried Rafael. ‘If you fall out and get stuck in the bottom of a waterfall, you’ll be pulled round and round under water till you drown. That’s if you don’t get your skull smashed open on a rock first!’

‘We’re going to avoid the rapids,’ said Dad. ‘The left branch of the river is completely safe.’

‘I’m going to check with the captain,’ said Rafael, clutching the map against his life jacket. ‘My pa will not be happy!’

As if on cue, the phone’s shrill ring cut through the air. Dad fished a bulky satellite phone from a pocket. ‘Yes. Senhor Santa Lucia. How are you, Senhor?’

‘WHERE ARE YOU, MANSELL? WHAT PROGRESS HAVE YOU MADE?’ Ben couldn’t help but hear the barking voice on the other end of the line, despite the noises in the background – it sounded as if Rafael’s dad was in a football stadium.

‘We made a slight detour,’ replied Dad. ‘And—’

‘WHERE ARE YOU?’ the voice shouted again. ‘Come on, referee! You blind? OUR AGREEMENT WAS THAT YOU FOLLOW THE MAP, MANSELL!’

‘Well, we’re not exactly on the route,’ said Dad calmly. ‘We’ve taken an interesting small deviation to the east, where—’

‘WHAT?!’

‘Well, as I explained earlier, Senhor, I’m concerned about the authenticity of the map you gave me, and if we widen our search area—’

‘THAT MAP IS AUTHENTIC!’

‘Well, with respect, several key landmarks have proved to be inaccurate, and—’

‘GOOOOOOOAAAAAAAL!’

Dad held the phone away from his ear with a grimace as a loud crackle of cheering poured out.

‘YOU FOLLOW – THE – MAP!’ went on Senhor Santa Lucia, once the din had subsided. ‘LANDMARKS CHANGE AFTER 500 YEARS – IT’S OBVIOUS! CALL YOURSELF AN ARCHAEOLOGIST? GET BACK ON TRACK AND CONTACT ME IN TWENTY-FOUR HOURS.’ The line went dead.

Dad let out a long breath as he put the phone away. He swore, shook his head, then pulled out some maps from a bag and powered up his laptop using his solar battery. ‘After the fork …’ Ben heard him mutter. ‘Eventually rejoin a tributary that will take us back on to the Senhor’s route …’