Nico spun, gently pushing Will to one side, and stuck his sword in that direction.

There was nothing.

‘What’s happening?’ Will demanded.

Nico brought his sword back close to his body. He turned to Will. ‘I think you got me all amped up, is all. I’m imagining things.’

Will didn’t look convinced. Unfortunately, Nico wasn’t surehebelieved it, either.

‘Okay,’ Will said. ‘But is it going to be this dark the whole time?’

‘Oh, no, not at all. We have to descend these steps for a while, but once we emerge in the Underworld, it’s … Well, you’ll see. This is the only part without any light.’ He paused. ‘At least, before we get to Tartarus.’

‘Good to know,’ Will muttered.

Nico headed down the narrow stairway, and Will followed. The steps were much steeper than Nico would have liked, but that was mostly because he was worried for Will. He could hear his boyfriend’s footsteps echoing around him – Will was tapping his feet on every step as if to make sure it was solid. After a few minutes, Nico paused.

‘You’re nervous,’ he said. ‘Just take the steps like you normally would. It’ll be all right.’

Will started to answer, then stopped and looked behind him. ‘Did you hear that?’

‘Hear what?’

‘Is something following us?’

Nico didn’t hear anything this time.

‘Maybe it’s your imagination?’ said Nico. ‘This place can feel very strange the first time.’

‘Okay,’ said Will, his voice shaky. ‘Lead the way, then.’

They continued. Will had Nico stop a few more times, but in each instance Nico couldn’t hear whatever it was his companion had. So they kept going, descending deeper and deeper. Nico knew that the stairway was lengthy, so he tried to remain as calm as possible as he put one foot in front of the other, careful not to slip on the slimy steps.

It wasn’t long before impatience began to creep along Nico’s spine. He remembered descending these same steps years ago whenhe had led Percy to his father. The memory stung a little; he hadn’t really wanted to betray Percy, but he’d needed to know more about his own childhood, which he’d lost in the River Lethe. But Nico recalled that it had maybe taken an hour or so to traverse the entire set of steps.

Had it been an hour since Will parted the stones? Or had it been longer? Weren’t journeys supposed to feel shorter when you’d done them before?

Will echoed Nico’s thoughts. ‘How much further do we have to go?’ he asked. ‘I feel like we’ve been going down forever.’

‘I think we’ve got a bit more,’ said Nico, panting. His arm was tired from holding out his sword; the last time he’d made this journey, Percy had been the one to light the way. Funny how the older Nico got, the more he saw things about Percy differently.

‘Like, I get that it’s theUnderworld,’ said Will. ‘So we have to go under the earth. But this –’

‘Shhh.’ Nico froze so suddenly that Will ran into him.

‘What is it?’ whispered Will.

‘Do you hear that?’

They both stood still. From somewhere ahead came a muted roar, like a rainstorm against a metal roof.

‘What is that?’ asked Will.

Nico smiled. ‘That’s the River Styx. We’re almost there.’

The two of them forged ahead. Nico began to take the steps two at a time. He nearly slipped on one of the stones, then steadied himself and waited for Will to catch up.

Soon, a dim grey light filled the tunnel. Nico did his best to keep his cool as they continued their descent. The roar of the Styx turned from muted to thunderous. The steps started to level out. When Nico reached the bottom of the stairwell, he emerged intoa large cavern lit by glowing stalactites overhead. To his right, the River Styx spilled over the edge of a towering climb and cascaded down a set of rocky rapids.