‘A hostile spirit, do you mean?’ said Cage.
‘If you insist, yes,’ said Jowett. ‘There are unknown forces just as powerful as electricity, we may be sure.’
‘Poppycock!’ said Dr Benjamin.
‘I beg your pardon,’ said Jowett.
‘Supernatural agency be blowed!’ said Dr Benjamin. ‘Brand was a charlatan. Have you never heard of Blue John?’
‘Blue John? He is not known to me.’
‘It’s a substance, not a person.’
‘I am at a loss to understand what you are talking about, Doctor.’
‘That’s obvious. Before the post mortem we were asked to pay particular attention to the hands of the deceased. On examination we found a number of minute particles adhering to the surface of the right palm. When we analysed them they proved to be crystals of calcium fluoride, or fluorspar- in layman’s language, Blue John. There is a quick method of identifying the fluoride ion, which we carried out, heating the substance in concentrated sulphuric acid and holding a plate of clear glass over it. The hydrofluoric acid so produced etched the glass, rendering it opaque. Blue John, without a doubt.’
Jowett was still shaking his head. ‘I fail to see-’
Dr Benjamin turned his eyes heavenwards, inviting everyone round the table to share his exasperation at Jowett’s incomprehension. ‘When Blue John is gently heated,’ he said, as if talking to a child, ‘he glows in the dark. Have you not heard of fluorescence? The spirit hand you saw was the medium’s, coated with fluor-spar, which he had warmed at the fire before the seance commenced. And if you don’t believe that establishes Brand as an impostor, you might reflect on the fact that under his normal clothes he was wearing a nightshirt, in the pocket of which we found a small bag of talcum powder. You obviously have a closer acquaintance with the spirits than I, but I believe that people who have encountered them have observed that in their manifested form they have white faces and long, flowing garments.’
Jowett was pale enough to have slipped on a nightshirt himself and caused havoc in the corridors of Scotland Yard. ‘We are-er-deeply in your debt Doctor. This is remarkable information. Greatly to be commended.’
‘We can’t claim much credit,’ said Dr Benjamin. ‘We were acting upon the suggestion contained in a note we received before the post mortem. It categorically requested us to examine the palms for Blue John.’
‘Really?’ said Jowett weakly. ‘Did you discover who wrote the note?’
‘It was one of your chaps, or we shouldn’t have acted upon it. A Sergeant Cribb.’
‘My godfathers!’ said Jowett. He turned to look at Cribb, who had seldom felt so uncomfortable.
‘I say, was it you?’ asked Cage. ‘You’re a quiet one, by Jove!’
‘How the devil did you know about Blue John?’ demanded Jowett.
Cribb had pledged himself to keep out of trouble by not saying a word.
‘Speak up, man!’ ordered Jowett.
That made it insubordination to remain silent. ‘I spent a few months in Derbyshire when I was in the army, sir. Blue John is also known as Derbyshire Spar. It’s common there.’
‘Well, you might have had the decency to stop me earlier, when I was talking about supernatural forces. Made me seem a confounded-never mind. This has been most instructive, of course, but it has brought us no nearer to ascertaining how Mr Brand met his death, unless the sergeant has some other information he has been keeping from us.’
Everyone looked in Cribb’s direction. He was acutely conscious of the delicacy of his position. Jowett must on no account be led to suppose that his thunder had been stolen again. ‘No information of any note, sir. Nothing more than a few theories.’
‘We had better hear them,’ said Jowett resignedly. ‘Mine has collapsed, so we may as well put yours to the test.’
‘I’m obliged to you, sir. It seems to me that if the electric chair works perfect now, as Mr Cage has indicated, it couldn’t have been working perfect at the moment Brand was electrocuted. Something must have happened to make it dangerous, something that was put right afterwards. So I’d like to ask Mr Cage if there was any way in which the main current could be made to by-pass the transformer.’
‘Only by disconnecting it and fastening the cable directly to the wires that were attached to the arms of the chair,’ said Cage. ‘Or I suppose another way might be to attach a wire to the positive terminal on the mains side of the transformer and connect it on the other side with one of the trailing wires. In either case it would have to be a deliberate act and it would amount to murder.’
‘Murder by electrocution,’ mused Dr Benjamin. ‘I’ve never heard of such a thing, but I suppose it’s possible. Who would want to murder a medium?’
‘Before we answer that,’ said Jowett, ‘there’s a question I should like to put to Mr Cage. If some malevolent person chose to tamper with the apparatus in one of the ways you have described would he not run the risk of electrocuting himself?’
‘If he tried it when the power was on, he would certainly kill himself,’ Cage confirmed.
Jowett spread his palms to signify the collapse of Cribb’s theory.
‘As I understood it,’ returned Cribb, looking steadily at the table in front of him as he spoke, ‘there was an interruption during the seance when Mr Brand claimed that someone had entered the study. Mr Nye went downstairs to turn off the current. It was not turned on again until Mr Brand was pacified. Shortly after, Brand was found dead in the chair.’
‘That is so,’ conceded Jowett, discountenanced again. ‘What I can’t explain is why he was not killed at the instant the power was restored,’ Cribb went on. ‘If I have it correct, the experiment was set up again at twenty minutes to eleven, the current was switched on and the galvanometer reading was not exceptional. It was a full minute before the needle jumped and we pulled aside the curtain to find Brand’s body.’
‘It makes no sense to me,’ said Cage.
‘There’s a notion forming at the back of my mind, but it’ll want time,’ said Cribb. ‘For the present, can we proceed upon the assumption that this was murder?’
‘If you think it will lead us somewhere,’ said Jowett, without much enthusiasm.
‘Well, sir, let’s return to the spirit hand for a moment.’
Jowett went a shade pinker.
‘If Brand was waving his right palm, coated with Blue John, about in the air-and it must have looked uncommon convincing, sir-he couldn’t have been holding the hand of the person on his right. In other words, the circle was broken and that person must have known it and been a party to the deception.’
‘By George, yes!’ said Jowett. ‘Do you know who it was? Miss Crush, of all people! I am absolutely certain of it.’
‘Rightly so, sir. Mr Strathmore very helpfully made a plan of the seating arrangements, which I borrowed on Saturday. Miss Crush, as you say, sat on the right of the medium and must have helped him. Now why should that lady be so rash as to conspire with a fraud-as we now know Brand to have been? He was not her class of person at all. You don’t find respectable maiden ladies with houses in Belgravia associating with the dregs of the race-course. There had to be some reason for this irregular alliance.’
‘I think I know it, Sarge,’ said Thackeray suddenly.
‘We’ll return to you in a moment, then,’ said Cribb without much gratitude. ‘I first suspected something between them when we attended Professor Quayle’s lecture. Already she had tried to persuade me not to question Peter Brand about the theft of her vase, although at the time I put that down to her enthusiasm for spiritualism, and her wish not to upset the medium. But at the lecture, it was crystal clear that she was there to help him, supplying him with information about Uncle Walter, and pretending it was all quite new, although they had been through the same performance at the first seance at Richmond.’