'I am sure that you mean kindly in speaking so,' said Maturin. 'Yet you must allow me to say that I wonder at it - I wonder that a man of your parts should believe in a simple, single cause for so complex an effect as a state of mind. Is it conceivable that mere absence of tobacco alone could make me testy? No, no: in psychology as in history we must look for multiple causality. I shall smoke a small cigar, or part of a small cigar, out of compliment to you; but you will see that the difference, if it exists at all, is very slight. Indeed, the springs of mood are wonderfully obscure, and sometimes I am astonished at what I find welling up from them - at the thoughts and attitudes that present themselves, fully formed, before the mental eye.'

It was quite true. The John Dory and the yearning for tobacco were not enough to account for Maturin's ill-temper, which in any case had lasted for some days, surprising him as he woke each morning. As he pondered it suddenly occured to him that at least one of the many reasons was the fact that he was sexually starved and that recently his amorous propensities had been stirred. 'The bull, confined, grows vicious,' he observed to himself, drawing the grateful smoke deep into his lungs: but that was not a full explanation, by any means. He moved out into the sun, to the leeward side of the arbour, so that he should not fumigate Professor Graham; and there, blinking in the strong light, he turned the matter over in his mind.

His move brought him into sight from the Apothecary's Tower, a tall, severe building with an incongruous clock in its forehead. Its gaunt, unfurnished topmost room had not been occupied since the time of the Knights; the floor was coated with soft grey dust and bat-dung, and in the dim rafters high overhead the bats themselves could be heard moving about, while all the time the clock ticked away the seconds in a deep, resonating tone. It was a cheerless, inimical room, yet it provided watchers with a fine view of the Baracca, of Searle's hotel and of its courtyard, though not, obviously, of its covered bowers. 'There is one of them,' said the first watcher. 'He has just moved into the sun.'

'The naval surgeon, smoking a cigar?' asked the second. 'He is a naval surgeon, and a very clever one, they say; but he is also an intelligence-agent. His name is Maturin, Stephen Maturin: Irish father, Spanish mother - can pass for either; or for French. He has done a great deal of damage; he has been the direct cause of many of our people's death and he was aboard the Ocean when your cousin was poisoned.' 'I shall deal with him tonight.'

'You will do nothing of the kind,' said the first man sharply. His Italian had a strong southern accent, but he was in fact a French agent, one of the most important French agents in the Mediterranean, and the Maltese with him bowed submissively. Lesueur was the Frenchman's name and he was not unlike a somewhat older version of the Dr Maturin whose face he was now examining so attentively with a pocket spy-glass; a slight man of under the middle height, sallow, stooping, bookish, with an habitually closed, reserved expression, a man who would rarely draw attention but who having drawn it would give the impression of more than usual self-possession and intelligence: and Lesueur also had the easy authority of one with great sums of money at his command. He was dressed as a fairly prosperous merchant. 'No, no, Giuseppe,' he said more kindly, 'I commend your zeal, and I know you are an excellent hand with a knife; but this is not Naples, nor even Rome. His abrupt, unexplained disappearance would make a great deal of noise - the implications would be obvious, and it is absolutely essential that our existence should not be suspected. In any event there is little to be learnt from a corpse, whereas the living Dr Maturin may supply us with a great deal of information. I have set Mrs Fielding on him, and you and Luigi will watch his other meetings with the greatest care.'

'Who is Mrs Fielding?'

'A lady who works for us: she reports directly to me or Carlos.' He might have added that Laura Fielding was a Neapolitan married to a lieutenant in the Royal Navy, a young man who had been captured by the French during a cutting-out expedition and who was now confined in the punishment-prison of Bitche for having escaped from Verdun; and as he had killed one of the gendarmes who were pursuing him it was likely that he would be condemned to death when his trial came on. But the trial was postponed again and again, and by an exceedingly roundabout route Mrs Fielding was told that it might be postponed indefinitely if she would cooperate with a person who was interested in the movements of shipping. The matter was put to her as having to do with international insurance - with great Venetian and Genoese firms whose French correspondents had the government's ear. The story might not have answered with anyone thoroughly accustomed to business, but the man who told it was a convincing speaker and he produced a perfectly authentic letter written by Mr Fielding to his wife not three weeks before, a letter in which he spoke of 'this exceptional opportunity to send his love and to tell his dearest Laura that the trial had been put off again - his confinement was now much less severe, and it seemed possible that the charges might not be pressed with the utmost rigour.

Mrs Fielding was well placed for the gathering of intelligence: not only was she very widely received, but to eke out her minute income she gave Italian lessons to officers' wives and daughters and sometimes to officers themselves, and this brought her acquainted with a good many pieces of more or less confidential information, each in itself trifling enough, but each helping to build up a valuable picture of the situation. In spite of her poverty she also gave musical parties, offering her guests lemonade from the prolific tree in her own courtyard and one Naples biscuit apiece; and this added to her value from Lesueur's point of view, for she played the piano and a beautiful mandoline, sang quite well, and gathered all the more talented naval and military amateurs in a singularly relaxed and unguarded atmosphere. Yet he had not made anything like full use of her potentialities until now, preferring to let her get thoroughly used to the notion that her husband's welfare depended on her diligence. Lesueur might have told Giuseppe all this without any particular harm, but he was a man as close and reserved as his face, and he liked keeping information to himself - all information. Yet on the other hand Giuseppe, who had been away for a great while, had to have some knowledge of the present situation: he also had to be humoured to a certain degree. 'She teaches Italian,' said Lesueur grudgingly, and paused. 'You see the big man in the arbour on the far left?'

'The one-armed commander in a scratch-wig?'

'No. At the other end of the table.'

'The great fat yellow-haired post-captain with that sparkling thing in his hat?'

'Just so. He is very fond of the opera.'

'That red-faced ox of a man? You astonish me. I should have thought beer and skittles more his line. Look how he laughs. They must surely hear him in Ricasoli. He is probably drunk: the English are perpetually drunk - do not know decency.'

'Perhaps so. At all events he is very fond of the opera. In passing, let me caution you against letting your dislike cloud your judgment, and against underestimating your enemy: the red-faced ox is Captain Aubrey, and although he may not look very wise at present he is the man who negotiated with Sciahan Bey, destroyed Mustapha, and turned us out of Marga. No fool could have done any one of those things, let alone all three. But as I was about to say, being here for some time and being fond of the opera, he decided to have Italian lessons so that he might understand what was going on.' Giuseppe was about to make some remark on the simplicity of this notion, but seeing the look on Lesueur's face he closed his mouth. 'His first teacher was old Ambrogio, but as soon as Carlos heard of this he sent proper people to tell Ambrogio to fall sick and to recommend Mrs Fielding. Let us have no interruptions, I beg,' he said, holding up his hand as Giuseppe's mouth opened again. 'She is already twelve minutes overdue and I wish to say all that I have to say before she comes. The whole point is this: Aubrey and Maturin are close friends; they have always sailed together; and by bringing the woman into contact with Aubrey I bring her into contact with Maturin. She is young, good-looking, quite intelligent, and of good reputation - no known lovers at all. No lovers since her marriage, that is to say. In these circumstances I have little doubt of his becoming involved with her, and I look forward to some very valuable information indeed.'