'So you don't remember what particular problem arose yesterday evening?'

'No, inspector, I do not.'

'When you arrived in your office this morning and found the safe door open, what was the first thing you did?'

'I checked to see what was missing.'

'And what did you discover?'

'All my cash had been taken.'

'How can you be sure it had all been taken?'

'Because I found this open envelope on my desk,' Hugo said, handing it over.

'And how much should there have been in the envelope, sir?'

'Sixty-eight pounds and ten shillings.'

'You seem very certain of that.'

'Yes, I am,' said Hugo. 'Why should that surprise you?'

'It's simply that Miss Potts told me there was only sixty pounds in the safe, all in five-pound notes. Perhaps you could tell me, sir, where the other eight pounds and ten shillings came from?'

Hugo didn't answer immediately. 'I do sometimes keep a little loose change in my desk drawer, inspector,' he said finally.

'That's quite a large sum to describe as "a little loose change". However, allow me to return to the safe for a moment. When you entered your office this morning, the first thing you noticed was that the safe door was open.'

'That is correct, inspector.'

'Do you have a key for the safe?'

'Yes, of course.'

'Are you the only person who knows the code and is in possession of a key, sir?'

'No, Miss Potts also has access to the safe.'

'Can you confirm that the safe was locked when you went home last night?'

'Yes, it always is.'

'Then we must assume that the burglary was carried out by a professional.'

'What makes you say that, inspector?' asked Barrington.

'But if he was a professional,' said Blakemore, ignoring the question, 'what puzzles me is why he left the safe door open.'

'I'm not sure I'm following you, inspector.'

'I'll explain, sir. Professional burglars tend to leave everything just as they found it, so that their crime won't be found out immediately. It allows them more time to dispose of the stolen goods.'

'More time,' repeated Hugo.

'A professional would have closed the safe door and taken the envelope with him, making it more likely that it would be some time before you discovered anything was missing. In my experience, some people don't open their safes for days, even weeks. Only an amateur would have left your office in such disarray.'

'Then perhaps it was an amateur?'

'Then how did he manage to open the safe, sir?'

'Maybe he somehow got hold of Miss Potts's key?'

'And the code as well? But Miss Potts assures me that she takes her safe key home every night, as I understand you do, sir.' Hugo said nothing. 'May I be allowed to look inside the safe?'

'Yes, of course.'

'What is that?' asked the inspector, pointing to a tin box on the bottom shelf of the safe.

'It's my coin collection, inspector. A hobby of mine.'

'Would you be kind enough to open it, sir?'

'Is that really necessary?' asked Hugo impatiently.

'Yes, I'm afraid it is, sir.'

Hugo reluctantly opened the box, to reveal a hoard of gold coins he had collected over many years.

'Now, here's another mystery,' said the inspector. 'Our thief takes sixty pounds from the safe, and eight pounds ten shillings from your desk drawer, but leaves behind a box of gold coins that must be worth considerably more. And then there's the problem of the envelope.'

'The envelope?' said Hugo.

'Yes, sir, the envelope you say contained the money.'

'But I found it on my desk this morning.'

'I don't doubt that, sir, but you will notice that it has been slit neatly open.'

'Probably with my letter opener,' said Hugo, holding it up triumphantly.

'Quite possibly, sir, but in my experience, burglars have a tendency to rip open envelopes, not slit them neatly with a letter opener as if they already knew what was inside.'

'But Miss Potts told me that you'd found the thief,' said Hugo, trying not to sound exasperated.

'No, sir. We have found the money, but I'm not convinced that we've found the guilty party.'

'But you found some of the money in his possession?'

'Yes, we did, sir.'

'Then what more do you want?'

'To be certain we've got the right man.'

'And who is the man you've charged?'

'I didn't say I'd charged him, sir,' said the inspector as he turned a page in his notebook. 'A Mr Stanley Tancock, who turns out to be one of your stevedores. Name ring a bell, sir?'

'Can't say it does,' said Hugo. 'But if he works in the yard, he would certainly have known where my office was.'

'I am in no doubt, sir, that Tancock knew where your office was, because he says he came to see you around seven yesterday evening to tell you that his brother-in-law, a Mr Arthur Clifton, was trapped in the hull of a ship being built in the yard, and if you didn't give the order to get him out, he would die.'

'Ah, yes, I remember now. I did go over to the yard yesterday afternoon as my ganger will confirm, but it turned out to be a false alarm and a waste of everyone's time. Clearly he just wanted to find out where the safe was, so he could come back later and rob me.'

'He admits that he came back to your office a second time,' said Blakemore, turning another page of his notes, 'when he claims you offered him sixty-eight pounds and ten shillings if he would keep his mouth shut about Clifton.'

'I've never heard such an outrageous suggestion.'

'Then let us consider the alternative for a moment, sir. Let us suppose that Tancock did come back to your office with the intention of robbing you some time between seven o'clock and seven thirty yesterday evening. Having somehow managed to get into the building unobserved he reaches the fifth floor, makes his way to your office, and with either your key or Miss Potts's unlocks the safe, enters the code, removes the envelope, slits it neatly open and takes out the money, but doesn't bother with a box of gold coins. He leaves the safe door open, spreads some of its contents on the floor and places the neatly opened envelope on your desk, and then, like the Scarlet Pimpernel, disappears into thin air.'

'It needn't have been between seven and seven thirty in the evening,' said Hugo defiantly. 'It could have been any time before eight this morning.'

'I think not, sir,' said Blakemore. 'You see, Tancock has an alibi between eight and eleven o'clock last night.'

'No doubt this so-called "alibi" is some mate of his,' said Barrington.

'Thirty-one of them, at the last count,' said the detective inspector. 'It seems that having stolen your money, he turned up at the Pig and Whistle public house at around eight o'clock, and not only were the drinks on him, but he also cleared his slate. He paid the landlord with a new five-pound note, which I have in my possession.'

The detective removed his wallet, took out the note and placed it on Barrington's desk.