“She’s a hummer,” he muttered.  “I’ll make her go when we get the hang of it.  Sit tight!”

They drove clumsily off, gathering speed at every yard.  Behind, in the shadow of the tower, the signalman lay dead.  Quest, half way to New York, stretched flat on his stomach, was struggling for life with knees and hands and feet.

2.

Mrs. Rheinholdt welcomed the Inspector with a beaming smile as he stepped out of his office and approached her automobile.

“How nice of you to be so punctual, Mr. French,” she exclaimed, making room for him by her side.  “Will you tell the man to drive to Mr. Quest’s house in Georgia Square?”

The Inspector obeyed and took his place in the luxurious limousine.

“How beautifully punctual we are!” she continued, glancing at the clock.  “Inspector, I am so excited at the idea of getting my jewels back.  Isn’t Mr. Quest a wonderful man?”

“He’s a clever chap, all right,” the Inspector admitted.  “All the same, I’m rather sorry he wasn’t able to lay his hands on the thief.”

“That’s your point of view, of course,” Mrs. Rheinholdt remarked.  “I can think of nothing but having my diamonds back.  I feel I ought to go and thank the Professor for recommending Mr. Quest.”

The Inspector made no reply.  Mrs. Rheinholdt was suddenly aware that she was becoming a little tactless.

“Of course,” she sighed, “it is disappointing not to be able to lay your hands upon the thief.  That is where I suppose you must find the interference of an amateur like Mr. Quest a little troublesome sometimes.  He gets back the property, which is what the private individual wants, but he doesn’t secure the thief, which is, of course, the real end of the case from your point of view.”

“It’s a queer affair about these jewels,” the Inspector remarked.  “Quest hasn’t told me the whole story yet.  Here we are on the stroke of time!”

The car drew up outside Quest’s house.  The Inspector assisted his companion to alight and rang the bell at the front door.  There was a somewhat prolonged pause.  He rang again.

“Never knew this to happen before,” he remarked.  “That sort of secretary-valet of Mr. Quest’s—­Ross Brown, I think he calls him—­is always on the spot.”

They waited for some time.  There was still no answer to their summons.  The Inspector placed his ear to the keyhole.  There was not a sound to be heard.  He drew back, a little puzzled.  At that moment his attention was caught by the fluttering of a little piece of white material caught in the door.  He pulled it out.  It was a fragment of white embroidery, and on it were several small stains.  The Inspector looked at them and looked at his fingers.  His face grew suddenly grave.

“Seems to me,” he muttered, “that there’s been some trouble here.  I shall have to take a liberty.  If you’ll excuse me, Mrs. Rheinholdt, I think it would be better if you waited in the car until I send out for you.”