“I’m not kidding,” Quest assured him.  “I’ve got a phototelesme at work here.  I’ve seen the bone all right.  French, this is interesting.  I must think it over.”

Quest hung up the receiver and rang off.  Then he turned towards his two assistants.

“Another finger from the Professor’s skeleton,” he announced, “has been found just outside his grounds.  What do you suppose that means?”

“Craig,” Lenora declared confidently.

“Craig on your life,” Laura echoed.  “Say, Mr. Quest, I’ve got an idea.”

Quest nodded.

“Get right ahead with it.”

“Didn’t the butler at Mrs. Rheinholdt’s say that Craig belonged to a servants’ club up town?  I know the place well.  Let me go and see if I can’t join and pick up a little information about the man.  He must have a night out sometimes.  Let’s find out what he does.  How’s that?”

“Capital!” Quest agreed.  “Get along, Laura.  And you, Lenora,” he added, “put on your hat.  We’ll take a ride towards Mayton Avenue.”

2.

The exact spot where the bone of the missing skeleton was discovered, was easily located.  It was about twenty yards from a gate which led into the back part of the Professor’s grounds.  The neighbourhood was dreary in the extreme.  There were half-finished houses, little piles of building materials, heaps of stones, a watchman’s shed, and all the dreary paraphernalia of an abandoned building enterprise.  Quest wasted very little time before arriving at a decision.

“The discovery of the bone so near the Professor’s house,” he decided, “cannot be coincidence only.  We will waste no time out here, Lenora.  We will search the grounds.  Come on.”

They advanced towards the gate but found it locked.  The wall was unusually high as though to obscure a view of anything that lay on the other side.  Quest noticed with interest that, in places where it had shown signs of crumbling away, it had been repaired.  He contemplated the lock thoughtfully and drew a little instrument from his pocket, an instrument which had the appearance of a many-sided key.

“Looks like storming the fortress, eh?” he remarked.  “Here goes, any way.”

The gate swung open with a single turn of the wrist.  Quest glanced for a moment at the lock and replaced the instrument in his pocket.

“The Professor’s not looking for visitors,” he muttered.  “Gee!  What a wilderness!”

It was hard to know which way to turn.  Every path was choked with tangled weeds and bushes.  Here and there remained one or two wonderful old trees, but the vegetation for the greater part consisted of laurel and other shrubs, which from lack of attention had grown almost into a jungle.  They wandered about almost aimlessly for nearly half-an-hour.  Then Quest came to a sudden standstill.  Lenora gripped his arm.  They had both heard the same sound—­a queer, crooning little cry, half plaintive, half angry.  Quest looked over his right shoulder along a narrow, overgrown path which seemed to end abruptly in an evergreen hedge.