“Do, old chap—­and please hurry; time is everything in this case.  Let me introduce you to your client. (Keep looking at the flowers, please, Sir Henry.) I have the honour to make you acquainted with Sir Henry Wilding, Cleek; he needs you, my dear fellow.”

“Delighted—­in both instances.  My compliments, Sir Henry.  By any chance that Sir Henry Wilding whose mare, Black Riot, is the favourite for next Wednesday’s Derby?”

“Yes—­that very man, Mr. Cleek; and if—­”

“Don’t get excited and don’t turn, please; our friend the policeman is looking this way.  What’s the case?  One of ‘nobbling’?  Somebody trying to get at the mare?”

“Yes.  A desperate ‘somebody,’ who doesn’t stop even at murder.  A very devil incarnate who seems to possess the power of invisibility, and who strikes in the dark.  Save me, Mr. Cleek!  All I’ve got in the world is at stake, and if anything happens to Black Riot, I’m a ruined man.”

“Yar-r-r!” yawned the elderly sea captain, rising and stretching.  “I do believe, constable, I’ve been asleep.  Warm weather, this, for May.  A glorious week for Epsom.  Shan’t see you to-morrow, I’m afraid.  Perhaps shan’t see you until Thursday.  Here, take that, my lad, and have half-a-crown’s worth on Black Riot for the Derby; she’ll win it, sure.”

“Thanky, sir.  Good luck to you, sir.”

“Same to you, my lad.  Good day.”  Then the old gentleman in the top hat and white spats moved slowly away, passed down the tree-shaded walk, passed the romping children, passed the Princess Louise’s statue of Queen Victoria, and, after a moment, vanished.  Ten minutes later, when Narkom and Sir Henry returned to the waiting motor, they found him seated within it awaiting them, as he had promised.  Giving Lennard orders to drive about slowly in the least frequented quarters, while they talked, the superintendent got in with Sir Henry, and opened fire on the “case” without further delay.

“My dear Cleek,” he said, “as you appear to know all about Sir Henry and his famous mare, there’s no need to go into that part of the subject, so I may as well begin by telling you at once that Sir Henry has come up to town for the express purpose of getting you to go down to his place in Suffolk to-night in company with him, as his only hope of outwitting a diabolical agency which has set out to get at the horse and put it out of commission before Derby Day, and in the most mysterious, the most inscrutable manner ever heard of, my dear chap.  Already one groom who sat up to watch with her has been killed, another hopelessly paralysed, and to-night Logan, the mare’s trainer, is to sit up with her in the effort to baulk the almost superhuman rascal who is at the bottom of it all.  Conceive if you can, my dear fellow, a power so crafty, so diabolical, that it gets into a locked and guarded stable, gets in, my dear Cleek, despite four men constantly pacing back and forth before each and every window and door