She looked at him, not quite grasping the purport of his words, but even as he said them they gave him confidence. If she was recalcitrant, he might threaten her.
"Except yourself, no one can ever throw light upon Sir Geoffrey's death. You must swear that you will throw none on it."
She did not answer, but sat like a statue of despair, as white as marble and as motionless. Already they were drawing near to Clapham Junction; ten or twelve minutes were all that were left for him to get the oath he must obtain.
"Think," he said swiftly. "Think what it might mean if a living soul knew that you were at that boathouse to-day. You—Sir Geoffrey's wife—living on money derived from a man whom you had feloniously married, engaged to be married again to a man who is twice a millionaire! What would be said? That you had everything to gain by the death of Sir Geoffrey Holt, supposing your identity became known, as it must be then: that you could hope for no help or forgiveness from him, and that as the wife of Sir Ross you would be rich beyond the dreams of avarice—and safe. They would find there motive enough for the crime, and would say that your hand fired the shot. And if you told the truth, and swore I did it, why should they believe you? Why should I, who have lived all my life upon Sir Geoffrey's bounty, kill the man upon whom I actually depend for my daily bread?"
Lavender stared at him with increasing horror. Could he possibly intend to shift suspicion on to her, or was he only putting into words what would be the general opinion if her presence at Fairbridge that afternoon became known? Melville read the doubt in her mind, and, with his fiendish cleverness, allayed her first uncertainty. To let that rankle might be to goad her too far, but he must appeal to her self-interest too.
"If it got to that, of course that would be the end of me," he said, "for I should have to confess that the deed was only mine, and I could not be taken alive. But think what you stand to lose: the income you have, the fortune you may have, your name, your reputation, possibly your freedom. You would be so involved in a scandal of bigamy and murder that in self-defence you would have to disappear. Lavender, it isn't only for my sake that I'm putting it all like this; I'm not asking you to do anything. I'm only imploring you for both our sakes to do nothing. Will you give me your solemn promise to hold your tongue for ever about to-day's work? Will you swear not to say one word of where we have been, or anything else, to any living soul? Will you, Lavender—will you?"
In sheer despair she retired from the unequal contest.
"I promise," she said. "I will be silent."
Melville could not repress a sigh of relief. It never occurred to him to doubt her reliability. She would keep her promise, he knew, and he would be safe. But there was no opportunity for further converse. They were at Vauxhall, and the man who collected their tickets got into the compartment and travelled with them to Waterloo.
At the terminus Melville put Lavender into a hansom.