‘Right, that wasn’t funny,’ he agrees.

We start to move again. I study the LOCUS displays. The tunnel entrance looms closer, like the mouth of a whale.

‘Range forty metres,’ Halimah announces. ‘Depth is steady at twenty metres.’

I glance at Ester, who’s standing on my right with her plate of baked goods. ‘How does theNautilusseem to you?’

‘Calm,’ she says. ‘Want a scone?’

Calm is good. And, yes, I want a scone.

I hear no groans or creaks, no cries of alarm from the corridors. Still, I imagine a thousand little leaks springing up all along the sub’s ancient hull plating.

‘Jack,’ I say, ‘make a pass through the ship, would you? Check on all hands.’

‘Aye.’ He looks relieved to have a job. He grabs a scone and runs off.

‘Tunnel entrance ten metres,’ Halimah says. ‘This’ll be tight.’

‘You understand how to steer this thing?’ Virgil asks.

The pipe organ plays a diminished chord, making us all flinch.

‘I mean … do you know how to steer this beautiful vessel?’ Virgil corrects himself.

‘I think so,’ Halimah says. ‘Nautilus, help me out here. Captain?’

It takes me a second to realize she’s asking me a question. I’m still not used to being called Captain.

‘Ahead slow,’ I say. ‘Course corrections at your discretion.’

‘Aye.’ Halimah turns a lever ever so slightly.

As soon as we reach the tunnel, a tremor rattles the bridge. Bubbles cascade over the forward windows.

I grip my armrests. ‘What was –?’

‘Explosion!’ Gem yells, a little louder than necessary. ‘N-not close, though. That was about …’ He fiddles with his controlsand his holosphere changes to a deep purple colour. ‘Whoa, that’s cool.’

‘Something about an explosion?’ I prompt.

‘Right, sorry. There was a detonation against the north rim of the atoll, about a kilometre away. Torpedo, maybe?’

‘Massive shock wave for a torpedo,’ Virgil says.

‘TheAronnax,’ Ester says.

That name is more unsettling than the organ’s diminished chord.

I want to believe that Luca and Ophelia blew our enemies out of the water, but I know we couldn’t be that lucky. More likely theAronnaxwas sending a warning shot, letting Lincoln Base know they mean business. At least the cave hasn’t collapsed on top of us yet.

‘Steady as she goes,’ I say.

Halimah takes us into the tunnel.

Outside the windows, the constellations of phytoplankton disappear. Only a metre above our heads, the ceiling of the lava tube slithers past, glistening in the purple glow of the bridge. Of course Nemo would make his lighting purple, I realize. The longest light waves, blue and purple, are the last colours to disappear underwater. I wonder if theNautilushas purple headlights. Or ye olde windshield wipers.

The holospheres at all the stations suddenly flicker and die.