"Tall as she is and tall as we are," he whispered, as they threaded in out of the crowds on the pavement, "we can spot her at twenty yards. Cautiously, now—she's making for the cab rank!"
They watched Lady Riversreade charter and enter a taxi-cab: in another minute it moved away. But it had scarcely moved when Matherfield was at the door of the next cab on the rank.
"You saw that cab go off with a tall woman in it?" he said to the driver. "There!—just rounding the corner, know its driver? Right!—follow it carefully. Note where it stops, and if the woman gets out. Drive slowly past wherever that is, and then pull up a bit farther on. Be sharp, now—this is——" he bent towards the man and whispered a word or two: a second later he and Hetherwick were in the cab and across the top side of Trafalgar Square.
"This is getting a bit thick, Mr. Hetherwick," remarked Matherfield. "Your clerk tracks his man to Vivian's on Friday night, we find Lady Riversreade coming out of Vivian's on Monday night. Now I shouldn't think Lady Riversreade, whom we hear of chiefly as a humanitarian, a likely sort of lady to visit Vivian's!"
"She came out of Vivian's, anyway!" replied Hetherwick.
"Then, of course, she'd been in!" said Matherfield. "But why? I should say—to have a meeting with Baseverie, or with somebody representing him, or having something to do with the business that took him to Riversreade Court. What business is it? Has it anything to do with our business? However, there's Lady Riversreade in that cab in front, and we'll just follow her to find out where she goes—no doubt she's bound for some swell West End hotel. And that knowledge will be useful, for I may want to see her in the morning—to ask a question or two."
"Somewhat early for that, isn't it?" suggested Hetherwick. "Do we know enough?"
"Depends on what you call enough," replied Matherfield dryly. "What I know is this: that man Granett was poisoned. He had on him a brand new five-pound note. That note I've traced as far as Vivian's, where it was certainly paid to some customer in change on the very day before Granett and Hannaford's deaths: Vivian's is accordingly a place of interest. Now I hear of a mysterious man visiting Lady Riversreade—the man is tracked to Vivian's—I myself see Lady Riversreade emerging from Vivian's. I think I must ask Lady Riversreade what she knows about Vivian's and a certain Dr. Baseverie, and, incidentally, if she ever heard of a place called Sellithwaite and a police-superintendent named Hannaford? Eh! But we're leaving the region of the fashionable hotels."
Hetherwick looked out of the window, what he saw seemed unfamiliar.
"We're going up Edgware Road," said Matherfield. He leaned out of the cab and gave some further instructions to the driver. "I don't want to arouse any suspicion there in front," he remarked, dropping into his seat again. "The probability is that she's going to some private house, and I don't want her to get any idea that she's followed. Ah!—now we turn into Harrow Road."