Li got up and paced slowly round the room. 'So you believe that the amoebas and the yrr are one and the same. We've found our adversary.'

'With two provisos,' Rubin added. 'First, we have to solve the DNA conundrum, and second, there has to be some kind of queen-yrr. No doubt the collective is highly intelligent, but I reckon the stuff we've got down there is only the executive part of the whole.'

'A queen-yrr? How do you envisage it?'

'Well, the same and yet different. A bit like ants. The queen-ant is an ant, but a special one. She's at the heart of everything. The yrr are swarming organisms, you see – collectives of amoebas. If Anawak's right, they embody an alternative evolutionary path for intelligent life, but something must be guiding them.'

'So if we were to find this queen…' Peak began.

'No.' Rubin shook his head. 'There's no point in fooling ourselves. There could be more than one – there could be millions. And if they're smart, they won't come anywhere near us.' He paused. 'But to be queens, they'd necessarily share the same basic principles as the rest of the yrr. They'd aggregate, and they'd have genetic memory. We're in the process of isolating a chemical that the amoebas give off as a signal to start aggregating. Oliviera and Johanson are on the brink of working out its formula. And you can bet that this chemical, this pheromone, will also cause the queens to aggregate with the yrr too. Scent is the key to yrr communication.' Rubin gave a self-satisfied smile. 'And it could be the answer to all our problems.'

'Thank you, Mick.' Vanderbilt inclined his head towards him graciously. 'You're in our good books again – for the time being at least. Even if you did screw up on the well deck.'

'That wasn't my fault.' Rubin sounded offended.

'You're in the CIA, Mick. In my team. And in my team the buck always stops with you. Did we forget to mention that when we hired you?'

'No.'

Vanderbilt shoved his handkerchief clumsily into his trouser pocket.

I'm glad to hear it. Jude's about to call the President so she'll be able to tell him what a good boy you've been. Thanks for paying us a visit. Now, run along back to work.'

FLAG COMMAND CENTER

Crowe and Shankar didn't look anywhere near as self-assured as they had when they'd decoded the first signal. Team morale was low, which was only due in part to the terrible events on the well deck. It was becoming increasingly obvious that no one understood the yrr's strategy.

'Why send us a message and then attack us?' asked Peak. 'Humans wouldn't do that.'

'You've got to stop thinking in those categories,' said Shankar. 'They're not humans.'

'I'm just trying to understand.'

'Well, you never will, if you keep basing your ideas on human logic,' said Crowe. 'Maybe their first message was a warning. We know where you are. That's what their reply comes down to.'

'Maybe it was a diversionary tactic,' suggested Oliviera.

'But what would be the point?' asked Anawak.

'To distract us?'

'From what? From the fact that they were about to light up outside like a Christmas tree?'

'It's not as crazy as it sounds,' said Johanson. 'They certainly achieved one thing. They got us thinking they were interested in dialogue. Sal's right: people wouldn't act like that, and maybe the yrr know it. So they lulled us into a false sense of security, showed themselves in all their glory, and while we were blithely expecting a cosmic revelation, they gave us a kick in the teeth.'

'Maybe sending them a couple of lousy math questions wasn't such a great idea,' said Vanderbilt to Crowe.

Crowe lost her cool. Her eyes flashed. 'Do you have a better suggestion?'

'It's not my job to make suggestions,' said Vanderbilt, spoiling for a fight. 'That's your job. Making contact is your responsibility.'

'Making contact with whom? You won't accept it's not a plot by rebel mullahs.'

If all you can achieve with your crappy messages is to give away our location, that's your problem and you're going to have to fix it. You sent the enemy detailed information about the human race. You practically told them to attack.'

'You have to know who you're dealing with before you can negotiate,' Crowe hissed back. 'It's about time you understood that, you moron. I need to know who they are, which is why I'm telling them about us.'

'All this message shit is a dead end-'

'For Christ's sake, we've only just started!'

'Just like your jumped-up SETI hogwash was a dead end too. Only just started? Well, congratulations – how many people are going to die when you really get going?'

'Jack,' snapped Li.

'This contact crap is-'

'That's enough! I don't want arguments, I want results. So let's hear from someone who's got something to report.'

'We've got something,' Crowe said sullenly. 'The second message is based around a formula, the chemical formula for water. We'll find out what the rest of it means in due course – if we're allowed to work in peace.'

'We've made a bit of headway too,' Weaver added.

'So've we!' Rubin was in there like a shot. 'We've made a massive leap forwards, thanks to the, uh, assistance of Sigur and Sue.' He coughed. 'Maybe you'd like to explain, Sue?'

'You're too kind,' she muttered. To the others she said, 'We've managed to isolate the chemical that causes the cells to aggregate. It's a pheromone, and we know how it works. Sigur can take the credit for that – he dared to do battle with the monster to get those tissue samples.'

She put a sealed container on the table. It was half full of a watery liquid.

'The yrr scent is in here. We've analysed it and we're able to synthesise it. The formula is surprisingly simple. We're still not a hundred per cent sure exactly how they use it to make contact or who or what initiates the aggregation. But assuming that something's able to trigger it – and, for the sake of argument, I'm going to call that something the queen – there's the question of how it summons millions and billions of free-floating amoebas who don't have eyes or ears. That's what this pheromone is for. Chemicals aren't especially suited for communication under water – the molecules disperse too quickly. But over short distances pheromone signals work brilliantly. And, as far we can tell, the amoebas' pheromonal communication is restricted to this one chemical. There's no language, just a single word: aggregate! We're not sure how they keep communicating after they've aggregated. All we can say for certain is that there's some form of information exchange. It's no different from a neural network computer or a human brain. The individual units need messengers working between them. In biology, they're called ligands. If a cell wants to pass information to another cell, it can't just wander over and tell it so it sends a message via the ligands to the other cell. And when the ligands get to the cell, it's like arriving at any civilised house: they come to a door with a bell – scientifically speaking, a receptor. The ligands ring the bell, and the message is carried through a cascade of signals to the centre of the cell, where the information is passed to the genome.'

She paused.

'The amoebas in the tank also seem to communicate using ligands and receptors. Of course, the idea that cells are like houses with doorbells and helpful messengers is a little misleading. Each cell emits not just one but a cloud of molecules, and cells don't just have a single receptor – they've got something in the region of two hundred thousand. That's how they pick up the pheromones and dock on to the collective. That's two hundred thousand doorbells to help them communicate with their neighbouring cells! It's pretty impressive. The process of aggregation takes place like a relay – one cell picks up pheromones from the collective and attaches itself to the neighbouring cells, all the time sending out new pheromones to reach the other cells floating in the water around it, and so it goes on. It progresses from the centre outwards. For the sake of simplicity, let's skip a few stages of the argument and contend that the cells we've been looking at are indeed our formidable enemy, the yrr.'