There was only one explanation which would account for this sudden purchase of a sea-going motor-boat. Manning and de Roda must have made up their minds that the time had arrived for their final effort. Believing that I should be alone in the house that night, they had evidently decided to seize the diamonds by force and to make a bolt for the continent, where their plans were no doubt already arranged. Having become suspicious of Christine, they had apparently taken the simple course of locking her in her own room, so that she should have no possible opportunity of communicating their designs to me.
The one weak point in their otherwise excellent scheme had been the old French servant. Her affection for Christine had manifestly over-ridden her fear of the others; and, while pretending to carry out their orders, she had secretly consented to assist her young mistress.
If only the suggested plan worked successfully, nothing would fit in better with my own arrangements. To get Christine and de Roda into our hands was, as Campbell had said, the first and most essential step in our future proceedings. By eight-thirty, or soon after, he and Bobby ought to be back from Martlesea, and matters would be enormously simplified if they were to find half of the opening task already accomplished.
I was under no delusion, however, with regard to the dangerous nature of the undertaking. Should Christine's attempt fail, she would be in greater peril than ever, while even if she succeeded it was more than probable that her escape would be immediately discovered. In that event the house might be attacked before Campbell and Bobby returned. It was impossible to foretell to an exact certainty what time they would arrive, and, with everything at stake, Manning was not the sort of gentleman to allow the grass to grow under his feet.
I took out my revolver, and, having emptied the contents, carefully tested its mechanism. There was a comforting efficiency about the ensuing click, click, click, which left nothing to be desired, and, picking up the cartridges one by one, I reloaded it in every chamber. After all, if it came to a fight, the odds would be in my favour. I am a pretty safe shot, and, unless they blew the whole place to pieces, I ought to be able to hold the house against half a dozen assailants. No one could force an entrance without exposing himself to a bullet, and I was cheerfully prepared to shoot both Craill and Manning at the very first opportunity that presented itself.
A glance at the clock showed me that it was close on half-past six. There were still two hours to spin out before the appointed time—a prospect which certainly demanded all the patience that I possessed. I took the precaution of going upstairs again and fastening my bedroom window, and then, having filled a fresh pipe, I settled down grimly to my long vigil.
With exasperating slowness the minute hand crept up to seven, and began to drag round again on its interminable circle. By the time it had reached eight the strain of sitting there and doing nothing had become unbearable—so much so, indeed, that if it had not been for the very emphatic warning contained in Christine's letter I could hardly have resisted the temptation of starting out for the landing-stage. Her instructions had been too definite, however, to admit of any doubt as to their importance, and I felt that it would be madness to run the risk of endangering the whole plan for the lack of a little extra self-control.
At last the half hour struck, and with a sigh of relief I got up from my seat. Being careful to avoid any unnecessary noise, I unlocked the front door, and for a moment I stood on the step, revolver in hand, taking a rapid survey of the garden. Viewed from there in the gathering dusk, it presented a singularly peaceful and deserted appearance. A faint rustic in the tree-tops was the only sound which disturbed the silence, and, closing the door quietly behind me, I set off across the lawn in the direction of the iron gate.
On reaching that point I came to a temporary halt. The path beyond—always a sombre and depressing place even in broad daylight—was now so dark as to be hardly distinguishable from the rest of the shrubbery.
I peered ahead into the blackness, listening intently, but except for the occasional creak of a branch everything was as still as the grave. It was about as uninviting a route as one could very well imagine, but there was no other method of getting to the boat-house unless I disobeyed Christine's instructions, and I had been along it too often to be in much fear of losing my way.