The cab with Mary Sartoris inside jolted along behind the other one, and presently Mary was greatly relieved to find that her horse was going the faster of the two. She bitterly blamed herself now for her folly in not waiting to see Beatrice, and still more so for trusting so important a letter in the hands of a mere servant.

But it was idle to repine over the thing now. The mischief had been done and the great thing was to repair it as soon as possible. As Mary's mind emerged from the haze in which it had been enveloped for the last few days, she began to see things more clearly. Now she realised that she had no settled plan of action when she set out to see Beatrice. She would have had to tell her everything or nothing had they met, and she could not have done this without making certain disclosures about her brother. She saw now that it would have been far better to have destroyed the letter and said nothing about it.

But then Mary could not tell a deliberate lie of that kind, and Carl Sartoris would have been pretty sure to have asked the question. He was pleased to regard his sister more or less in the light of a fool, but he did not trust her any the more for that.

Mary lay back in the cab and resigned herself to the inevitable. It was good to feel that she was leaving the others behind now, and her spirits rose accordingly. If she could only get to Wandsworth before the precious pair, she would be all right, provided always that Beatrice had not been in front of her. But as most of the trains were usually late there was more than a chance of success in this direction. The girl was nearing her destination now. She lifted the shutter on the top of the cab and asked if the other cab was at any distance. There was a queer sort of a grin on the cabman's face, as he answered.

"About five hundred yards, miss," he said. "Something seems to have gone wrong with them. So far as I can see the cab has lost a tire."

The other cab had stopped, and something like an altercation was going on between the fare and the driver.

Mary had not far to go now, and she decided that it would be safer to walk the rest of the distance. There was a little crowd gathering behind her and a policeman's helmet in the centre of it. Truly fortune was playing on her side now.

It was not very far to the house; there it stood dark and silent, with no light showing in the garden in front. Mary felt pretty sure that she was in time. Then the front door of the house opened, there was a sight of the hall in a blaze of light, and in the foreground the figure of a woman standing on the doorstep.

Mary gave a groan and staggered back with her hand to her head.

"What a piece of cruel misfortune," she exclaimed passionately. "Another minute and I should have been in time. Why did I not drive up to the house? My over-caution has spoilt it all. I am sure that was Beatrice Richford."

The door of the house closed and the figure of the woman disappeared inside. Mary had had all her trouble for nothing. Not only was Beatrice more or less of a prisoner there, but those thieves were pressing on behind. What was the best thing to be done now, with Beatrice exposed to the double danger? Mary racked her weary brains in vain. And in a few minutes at the outside the others would be here. It seemed impossible to do anything to save Beatrice from this two-edged peril. Mary started as she caught sight of a figure coming up the front garden. It was a stealthy figure and the man evidently did not want to be seen. As he caught sight of Mary he stopped. It was too dark to distinguish anything but his outline.

"Beatrice," the man said in a tone of deep relief. "Thank God, I have come in time."

Mary did not know whether to be pleased or alarmed. Evidently this man was some friend of Beatrice who had obtained an inkling of her danger and had come to save her. On the whole it seemed to Mary that she had an ally here.

"I am afraid you are mistaken," she whispered. "I am not Beatrice Richford. But I am doing my best for the young lady all the same. She is——"

"Don't say that she is in the house?" the man said in a muffled tone.

"Alas, that I can say nothing else," Mary replied. "I was just too late. Mrs. Richford had just entered the doorway as I came up. If you will tell me your name——"

"Perhaps I had better," the stranger said after a minute's hesitation. "I am Mark Ventmore; perhaps you have heard of me."

Mary gave a little sigh of relief. She knew all about Mark Ventmore. Here indeed was a man who would be ready to help her. She drew a little nearer to him.

"And I am Mary Sartoris," she said. "If you have heard of me——"

"Oh, yes, you are the sister of that—I mean Carl Sartoris is your brother. But surely you are altogether innocent of the—the strange things that——"

"I am innocent of everything," said Mary passionately. "I have wasted my life clinging to a man in the faint hope of bringing him back to truth and honour again. I am beginning to see now that I am having my trouble for my pains, Mr. Ventmore. Suffice it for the present to say that Mrs. Richford stands in great peril."

"Oh, I know that," Ventmore said hoarsely. "I got that information from Bentwood, the scoundrel! At the instigation of Inspector Field, who has pretty well posted me on recent doings, I have been following that rascal pretty well all day. We won't say anything about Berrington, who I understand is more or less of a prisoner in your brother's house, because Berrington is the kind of man who can take care of himself. But Beatrice is in peril—Bentwood told me that. The fellow's brains are in a state of muddle so I could not get the truth from him. It was something about a case of diamonds."

"Yes, yes," Mary said. "The diamonds that Mr. Richford gave his wife for a wedding present. Mr. Richford has got himself into severe trouble."

"Richford is a disgraced and ruined man. The police are after him."

"So I gathered. He is now in the disguise of an elderly clergyman, and at present he is——"

"Hiding in that house at Edward Street," Mark cried. "I saw him with Bentwood. But what has he to do with those diamonds?"

"Everything. I overheard the plot laid," Mary proceeded to explain. "Mr. Richford went to his wife and demanded the diamonds. He wanted to raise money so that he could go away in comfort and luxury. He told his wife exactly how he was situated. She refused to comply with the request on the ground that the stones belonged to Mr. Richford's creditors. Then unhappily, Mrs. Richford withdrew the diamonds from the custody of the hotel officials, being afraid that there would be a bother over them or something of that kind. Richford watched her do it. Then he met two accomplices who recently passed as General Gastang and Countess de la Moray, and the plot was laid. Mrs. Richford was to come here."

"But in the name of fortune, why was she to come here?" Mark asked.

"Perhaps I had better be a little more candid with you," Mary sighed. "There is a scheme on foot between my brother and some of the gang to gain possession of certain papers that belonged to Sir Charles Darryll. There are keys, too, which Mrs. Richford is known to possess. I don't quite know what the scheme is."

"Anyway I can give a pretty good guess," Mark said. "My father has been very ill and he sent for me. We have not been very good friends, my father and I, because I turned my back on the city for the sake of art. But all that is past now, and we have become reunited. My father seems to know a great deal about Sir Charles's affairs—something about a ruby mine or something of that kind. Anyway, I'm to get my information from Mr. Fleming, who is my father's solicitor. But I am afraid that I am interrupting you."

"There is not much more to tell," Mary went on. "Colonel Berrington was induced to write a letter to Mrs. Richford asking her to come here and see my brother."

"Berrington must have been mad to think of such a thing!"

"No, he did it at my instigation. I managed to communicate with him and assure him that no harm should come of it. No harm would have come of it if I had only kept my head and done the right thing. But the fact remains that Mrs. Richford is in there; she has those diamonds in her pocket and the thieves are on the track. It seems to me——"

Mary did not finish the sentence, for Mark held out a hand and pulled her behind a bush, just in time, as two other people came up the path. There was no occasion to tell either of the watchers that here were the people of whom they were talking. The man Reggie and the woman Cora were standing on the doorstep whispering together. It was quite a still night and the other two behind the bushes could hear every word that was said.

"So far, so good," the man was saying. "We've got here and we are pretty sure that our bird is securely caged, but what next?"

"Wait our chance," the woman said with a certain fierce indrawing of her breath. "We can appear to have come here by accident, for instructions, anything. So long as Sartoris does not know about those stones we are safe. When we get them——"

"When we get them, Richford can whistle for his share of the money," the man said coolly. "By this time to-morrow we shall be in possession of more money than we have ever had before. I don't like this present business, it's far too dangerous. Unless we go so far as to murder that fellow Berrington and get him out of the way——"

"Don't," the woman said with a shudder. "I hate that kind of work. Anything clever or cunning, anything requiring audacity, I can do with. But violence!"

She shuddered again, and the man laughed softly as if greatly pleased with some idea of his.

"There is going to be no more violence or anything else," he said. "This game has got far too dangerous. We'll change those stones into money and then we'll quietly vanish and leave our good friend Sartoris to his own devices. What do you say to that?"

"Amen, with all my heart," the girl said. "The sooner the better. But don't forget that we have not yet settled on a plan of action."

"Leave it to chance," the man replied. "We have all the knowledge that is necessary to the success of our scheme, and the girl knows nothing. She will not stay very long, it is getting late already. Suppose we pretend that we have a cab waiting to take us back to town, and suppose that we offer to give her a lift. Then that scent of yours——" The woman called Cora laughed and clapped her hands gleefully. It was an idea after her own heart. She patted her companion affectionately on the shoulder.

"Come along, then," she said. "Open the door with your latchkey. It's getting cold and I am longing for something to eat. This kind of thing makes me hungry."

The door opened and then closed again softly, and the conspirators had vanished. With a gesture of anger Mark strode towards the house, Mary following.

"What on earth are you going to do?" she said anxiously. "Will you spoil everything by your impatience? If you only realized the dangers that lie hidden yonder!"

Mark paused abruptly and bit his lip. The trouble was not over yet.