“‘What’s that ring?’ she asked sharply.

“‘It’s an amethyst,’ he replied.

“‘I mean,’ she persisted, ‘what are you doing with it?’

“‘Nothing. Someone asked me to tell them what it’s worth, that’s all.’

“‘Give it back, Jack. Don’t get involved.’

“‘I’m not involved in anything,’ he protested. ‘I’ll give it back, Annie, don’t you worry.’

“Something in his tone reassured her, and although she was still anxious, she went back to bed and fell fast asleep. In the morning, when she woke, she saw to her surprise that her husband was not in bed, and when she went downstairs she found that he was nowhere about and the front door had been unlocked. There are two keys for the front door. One of them is usually left in the lock, and the other, the spare one, is kept on a hook behind the bar. Both keys were in their usual places that morning. All that day, Mrs Prentice waited for her husband to return from wherever he had gone, but he never came. This, she says, is very unlike him. For the last dozen years – ever since his spell in prison, in fact – he has been diligent and hard-working and always attentive to his wife’s concerns. He has never before taken himself off Without telling her where he was going.

‘‘By the late afternoon she was very anxious at his continued absence and went along to the local police station, which is not far away, to enquire if they had heard anything. They were unable to shed any light on the matter, but took down all the details she gave them and recorded her husband as a ‘missing person’. When she got home, however, and gave it all more thought, she decided she was not satisfied with the police response. She suspected that, because of her husband’s criminal record, they would do nothing, but simply wait for him to turn up. She therefore determined to take the matter into her own hands. No doubt, like the Carter-Smythes, she had heard my name mentioned somewhere, so she left Maria in charge of the pub and came to consult me.

“It was too late that evening for me to do anything much, but I made a note of the main facts, and the following morning – that is, yesterday – I went down to Rotherhithe to look into the matter. As you will imagine, I questioned Mrs Prentice closely on any aspect of her husband’s affairs that might prove relevant, and stressed to her that she must answer me truthfully.

“‘Do you believe that Elias Dack and his cronies have been trying to get your husband to help them dispose of stolen goods?’ I asked her.

“She nodded her head. ‘It must be that,’ said she. ‘You see,’ she explained, ‘although Jack himself hasn’t been to sea for a dozen years or more, he knows an awful lot of men as do make their living that way. It’s not just the men he knew when he was a sailor himself, neither. We gets all sorts coming in The Seven Stars, and Jack’s a good landlord and often stands talking to them in the tap room for hours on end. I doubt there’s anyone who knows more seafarers – both straight and crooked – than Jack, and I’m sure there’s plenty as would do a job for him for a small consideration, no questions asked.’

“‘Have you come across that amethyst ring anywhere?’ I asked.

“‘No, I haven’t,’ she replied, ‘and I’ve had a good look round. Jack must have taken it with him. To tell the truth, I hope he has taken it and given it back. But I’m worried that if he’s told them he doesn’t want anything to do with them, there might have been violence done and Jack might be hurt. I wouldn’t put anything past Dack, or that evil devil, Vokes.’

“‘Did you see what Jack was writing on that paper on Monday night?’ I asked her.

“‘Not at the time I didn’t; but I found it the next morning, where he’d left it in the tap room. I can’t make any sense of it, though,’ she added, as she handed me the sheet of paper. ‘As you see, Mr Holmes, it’s just ticks and odd letters.’

“This is the paper, Watson,” said Holmes, taking a folded sheet from between the pages of his notebook and passing it to me. “It is a singular document, is it not?”

I unfolded the sheet upon my knee and studied it for a few moments. There were five rows of symbols, as follows:

V I I I I I I – B C O

      V I I I I I – M N A B

   V I I I I – H B L

            V I I I – A R H A R

          V I I – O L G M

“I can’t think what it might mean,” I said at last.

“I think we may safely dismiss Prentice’s claim that he was estimating the value of the ring,” said Holmes. “That was, I take it, the merest humbug, something he made up on the spur of the moment for his wife’s benefit. Yet it is evident he was working something out.”

“The marks at the beginning of each line look rather like Roman numerals,” I suggested, “in which case the first group would represent eleven, the second, ten, and so on.”

“I agree,” said Holmes, “although, of course, as ‘eleven’ is usually represented by an ‘X’ followed by an ‘I’, and ‘ten’ simply by an ‘X’, his use of the numerals must be non-standard in some way. What do you make of the other letters, Watson?”

“They may be the initials of something, or of someone, I suppose,” I responded. “Perhaps if – despite what he told his wife – Prentice was considering helping Dack to smuggle stolen goods abroad, he was listing the initial letters of ships that he knew would be setting sail shortly. In which case,” I added, “the figures at the beginnings of the lines may represent dates – the seventh, eighth, ninth, tenth and eleventh of next month.”

Holmes nodded. “It is possible,” said he, “although I doubt whether even Prentice – however well informed he may be about sailors and ships – would know the departure dates of so many different vessels several weeks hence.”

“What then?” I asked. “Do you regard this paper as of any significance to the case?”

“Yes, I do, Watson. It was, after all, the last thing Mrs Prentice saw her husband attending to before his mysterious disappearance. I have a hypothesis, but it is somewhat tentative at present, and it is this I am hoping to either confirm or reject today. But, to continue my account, Mrs Prentice showed me a brass candlestick which stood on a shelf above the fireplace in the tap room.

“‘There should be two of these here,’ she said, ‘but when Jack went off, he took the other one with him.’

“I picked it up and examined it. The base was hollow, and I wondered for a moment if Prentice might have hidden something in the base of the missing one – something, perhaps, which he did not wish his wife to see. But, of course, that would not explain why he had needed to take the candlestick with him; he could simply have removed whatever he had hidden there, and put it in his pocket, before leaving the house.

“I then took myself along to the local police station, where I am fairly well known, especially after the help I was able to give Inspector Quirke in a forgery case last year in Lavender Yard. Quirke was on duty, and when I mentioned Prentice’s disappearance to him, he admitted to me that they were taking an interest in the matter, although he said they knew no more about it than they had heard from Prentice’s wife. However, information they have received in recent weeks has led them to believe that Rotherhithe is once more becoming a major staging post in the disposal of stolen goods, and he suggested to me that Prentice’s disappearance might be connected with that in some way. Although our conversation was an affable one, I sensed as we spoke that the inspector was holding something back, and I strongly suspect that the police have some plans afoot, which he did not feel able to confide in me. What they might be, I do not know. Anyway, having exhausted that source of information, I spent the rest of the day making general enquiries in the district, and interviewing people whose names Mrs Prentice had given me, without advancing my knowledge to any significant degree. It was only when I was on my way home, and was able to consider the whole business afresh in a detached manner, that I began to see my way to forming a hypothesis. It is this that I shall shortly put to the test, for we are nearly there.” As he spoke, our train plunged into a long dark tunnel, where the thud and clank of the engine boomed around the close brick walls. “This is the Thames tunnel,” said he. “We shall be at Rotherhithe in a minute.”