"Old Oppner's big Panhard in front. Going our way--Embankment is 'up.' I wonder what his Agency men are driving at? Alden's got something up his sleeve, I'll swear." "I'd like a peep inside that car," said Sheffield. Harborne took up the speaking-tube as the cab, in turn, rounded into Great Smith Street. "Switch off this inside light," he called to the driver, "and get up as close alongside that Panhard ahead as you dare. She's not moving fast. Stick there till I tell you to drop back." The man nodded, and immediately the gear snatched the cab ahead with a violent jerk. At a high speed they leapt forward upon the narrow road, swung out to the off-side to avoid a bus, and closed up to the brilliantly-lighted car. It was occupied by two women in picturesque evening toilettes. One of them was a frizzy haired soubrette and the other a blonde. Both were conspicuously pretty. The fair girl wore a snow white orchid, splashed with deepest crimson, pinned at her breast. Her companion, who lounged in the near corner, her cloak negligently cast about her and one rounded shoulder against the window, was reading a letter; and Harborne, who found himself not a foot removed from her, was trying vainly to focus his gaze upon the writing when the fair girl looked up and started to find the cab so close. The light of a sudden suspicion leapt into her eyes as, obedient to the detective's order, the taxi-driver slowed down and permitted the car to pass. Almost immediately the big Panhard leapt to renewed speed, and quickly disappeared ahead. Harborne turned to Inspector Sheffield. "That was Miss Zoe Oppner, the old man's daughter." "I know," said Sheffield sharply. "Read any of the letter?" "No," admitted Harborne; "we were bumping too much. But there's a political affair on to-night in Downing Street. I should guess she's going to be there." "Why? Who was the fair girl?" "Lady Mary Evershed," answered Harborne. "It's her father's 'do' to-night. We want to keep an eye on Miss Oppner, after the Astoria Hotel business. Wish we had a list of guests." "If Severac Bablon is down," replied Sheffield; grimly, "I don't think she'll have the pleasure of seeing him this evening. But where on earth is she off to now?" "Give it up," said Harborne, philosophically. "Oh, she of the golden hair and the white _odontoglossum_," sighed the little Frenchman, rolling up his eyes. "What a perfection!" They became silent as the cab rapidly bore them across Vauxhall Bridge and through south-west to south-east London, finally to Dulwich Village, that tiny and dwindling oasis in the stucco desert of Suburbia. Talking to an officer on point duty at a corner, distinguished by the presence of a pillar-box, was P.C. Dawson in mufti. He and the other constable saluted as the three detectives left the cab and joined them. "Been here long, Dawson?" asked Sheffield. "No, sir. Just arrived."