The Grail Murders

its sharpness tinged with mercury.' 'So?' I began slowly, trying to assemble all the facts.
    'So,' Benjamin continued. 'I suspect Bowyer's and Southgate's horses were fed a rich diet of oats and bran both last night and this morning. Now you know, Roger, how that would affect an excitable horse who has had little strenuous exercise? It would become fiery and restless, something I noticed when Bowyer and Southgate left for the hunt. However, can you imagine what would happen if such a horse was not only spurred but goaded by a spur tinged with mercury?' 'It would bolt.' 'Which is what happened.'
    'But, Master, Bowyer and Southgate, for all their faults, were expert horsemen. Why didn't they just dismount?'
    'Ah! But what if the stirrups of their saddle had been changed, each being given a narrower set? Now, when you mount a horse, you simply push your boot in to the stirrup. That's the easy part. It's like anything else: you can get a small ring on your finger, the problem is getting it off. Remember, Bowyer's and Southgate's boots were wet and so leather would swell a little. Now, as they left Templecombe, the boots fitted snugly. They would not object to such a tight fit, in fact it would help them keep their restless horses under control, but once they had set spurs and the horses bolted, murder occurred.' He shook his head. 'There's no proof. Bowyer's and Southgate's saddles have now been returned to the stable and the original stirrups probably replaced. Nevertheless, that is how I believe the trap was set.' 'But the spurs would be kept in their own chambers?' Benjamin shrugged. 'I don't think that need bother us. There are probably keys to fit every chamber in this house. It would take only a few minutes to open a door, search out the riding boots and pour a little mercury over each spur.' 'And the murderer?'
    'A vague suspicion as yet but I tell you this: if the murderer strikes again, it will be against us, Roger, so be on your guard!' 'What about Mandeville?' Benjamin peered at me.
    'He could be the murderer, Master. He knew where those agents were in London and about Mistress Hopkins. He could have killed his own men, Cosmas and Damien. Above all, he survived the hunt.'
    'An allegation's one thing,' Benjamin snapped. 'Proving it is another.' 'And the riddle? Have you really resolved it?'
    'Perhaps. I have remembered my schooling: baptism is often called "Jordan's water" after the river where Christ himself was baptised.' Benjamin grinned at my puzzlement. 'But let's leave that for the moment. More importantly, I can prove how Cosmas and Damien died. No ghostly intervention but a most subtle assassin.' He grasped me by the shoulder. 'Listen, Roger, go for a walk in the grounds or try and pour more balm on Mandeville's troubled spirit. Visit poor Southgate, flirt with young Mathilda, but come back here,' Benjamin peered out of the window, 'in about two hours.'
    I did what my master asked, trailing around the house like a ghost though no one really wished to speak to me. Rachel had gone to her own chamber. Santerre and his wife were in close council with each other. Mandeville still sulked in the hall whilst the old beldames in Southgate's chamber cackled with laughter and asked if I wanted them to wash me? Of Mathilda there was no sight whatsoever and I realised that Bowyer's death had panicked many of the servants into leaving Templecombe.
    I went down to the lakeside and stared across at that mysterious island. I wondered if I should climb into a barge and pole myself across but the mists still hung over the water, I was cold, frightened, and so, following Benjamin's instructions, returned to my own chamber.
    I found the door unlocked as I had given my master the key before I left; the light was poor but I could see nothing had been disturbed so lay down on the bed, pulling the curtains around me. I was half-dozing when suddenly I smelt something burning, followed by a small bang under my bed which shook me awake. I pulled back the curtains and dashed out of the room to find Benjamin standing there, laughing at my shock. ‘For God's sake, Master, what are you doing?' I bellowed.
    Benjamin patted me on the shoulder. 'Stay calm, Roger, I could have blown you up but I didn't. Here.' He walked back into the room. 'Help me push your bed away.'
    We did so, heaving and pushing until the bed moved a few inches and I saw the slight scorch mark on the stone floor beneath. Benjamin pointed to it.
    'I think that's how