Thankfully, I don’t get much time to brood. The crew keepsme busy whenever they find something that needs opening, which happens roughly every six seconds. Among our finds: the weapons bay, with a complement of four very old but probably still dangerous alt-tech torpedoes. We decide to leave those alone for now and hope they don’t blow up.

The dive chamber has a dozen sets of nemonium-mesh dive suits, helmets and tanks. Just cleaning these, figuring out how they work and testing them for usability could take another month.

On the bottom level of the sub (there are three levels total), we find a shuttle bay with a smaller mini sub nested inside.

‘That’s the skiff,’ Ophelia informs me. ‘And, no, we haven’t tried it yet.’

She shrugs and blows a strand of grey hair from her eyes. I’m starting to appreciate just how much work she and Luca have done on theNautilus, and how much remains to be done.

The skiff itself is fascinating. It has seats for two, under a transparent dome that is sleeker in profile than the eyes on the bridge. The body construction is likewise smooth and hydrodynamic, with small pectoral stabilizers and a tapered serrated tail. It looks like it was modelled after a bluefin tuna, one of the fastest fish in the world. How it moves, though, I can’t imagine. I see no room for any kind of engine.

On an external inspection of the hull, scuba divers Kay and Tia discover a large hollow sheath on the underbelly of the sub, like a cross between the open mouth of a baleen whale and the air intake on a fighter jet, but no one can figure out what it’s for. Like most of our other discoveries, we don’t mess with it.

By the evening, the crew is exhausted but still buzzing with excitement. They can imagine a future for HP again, at Lincoln Base. We’ll work on theNautilusall summer, or longer if need be, taking our time to learn the submarine’s secrets. We can putits technology to use, building up an unbeatable edge against Land Institute. Then … Well, then we will have options. We can come out of hiding, let our loved ones know we survived. We can rebuild our school and hold LI accountable for their attack.

I don’t trust these dreams any more than I trust theNautilus. But I smile and nod and let the others talk. I think about what Gem told me – how he’s glad I’m in charge. Why, then, do I feel like such a fraud?

For dinner, our orangutan chef feeds us homemade seaweed gnocchi in creamy lemon garlic sauce, followed by a delicious tiramisu cake. Because clearly we all need more caffeine and sugar.

Afterwards, Jupiter is in such a generous mood he lets some of the crew switch offThe Great British Bake Offso they can play retro games on the PlayStation and GameCube. Others volunteer to return to theNautiluswith Luca for some nighttime ‘detail work’. I’m not sure what that means. I’m afraid tomorrow morning I’ll find theNautilus’s hull decorated with airbrushed flames.

I don’t even see Nelinha until bedtime. Ester is already snoring when my Cephalopod friend arrives, grinning and covered in machine grease.

‘Luca says we’ll take theNautilusfor a short spin tomorrow,’ she whispers to me, ‘if you can convince it to move!’

I suppose I should be thrilled. I might achieve what every Dakkar since the 1800s has dreamed of: getting theNautilusback into action.

‘Yeah.’ I try to sound enthusiastic for Nelinha’s sake. ‘That would be amazing!’

But I go to sleep more unsettled than ever.

I feel like someone has openedmybrain’s access panels and started cleaning out all the excess goop. I’m not sure I wantthem in there, removing the residue and debris of my life. Who will I be when they’ve finished their repairs?

While I sleep, I have more nightmares about being trapped and drowning. Only this time my underwater tomb looks like the bridge of theNautilus.

The next morning, I’m up early again to dive.

Socrates is nowhere to be seen. In fact, the lagoon seems devoid of any dolphins. This doesn’t help my sense of foreboding.

At breakfast, my classmates are in good spirits. Trying to sail theNautiluswill be the most challenging thing we’ve ever done, and I can practically smell the adrenalin in the air, along with the scent of Jupiter’s blueberry muffins.

Linzi Huang reports that last night in the sickbay, Dr Hewett farted in his sleep. Apparently, this means his bodily systems are working better. She jokes that he’ll be lecturing us again in no time. Cooper Dunne claims he had a dream about how to fix theNautilus’s torpedoes. His fellow Sharks tease him about doing his best thinking while he’s unconscious. Kay Ramsay, who hasn’t smiled since she lost her sister in the attack on HP, actually laughs at one of Robbie Barr’s corny jokes – something about how many nuclear engineers it takes to change a light bulb. Cephalopod humour – I don’t get it.

Some of the crew are whispering about how creepy the old sub is, which just makes them more excited. A few gossip about where Captain Nemo’s body was found, and how exactly my parents were killed. They try to have these conversations out ofmy earshot, so as not to upset me. Unfortunately, I can read lips.

Everybody seems to think that our first spin in theNautiluswill be a great success.

‘You’ve got the Nemo touch!’ Kiya Jensen tells me, as if she wasn’t questioning my taking command of theVarunajust a few days ago.

Even Nelinha, who knows how tricky advanced tech can be, seems perfectly at ease. ‘We are about to operate the oldest, most complicated submarine on the planet,’ she says. ‘Aren’t you even a little excited?’

I don’t know how to answer her. These days, I’m having trouble distinguishing between excitement and terror.

After cleaning up from breakfast (because time, tide and dirty dishes wait for no one), we gather on theNautilus’s dock for a pre-dive briefing. The Cephalopods have brought their tool kits. The Sharks have brought their weapons. Gemini Twain has so many guns and other dangerous objects strapped to his body he looks like he’s expecting to fight off a mermaid apocalypse.

He catches me looking and shrugs like,You never know.

TheNautilusherself appears unchanged since yesterday. No flames have been painted on her prow, thank goodness. Her giant insect eyes glint in the dim light of the cavern. In the water around her, the multicoloured phytoplankton are still putting on their Holi festival.