ns when there was heard an
uncompromising double knock at the street door, followed by the loud
pealing of a bell in the basement.

"Bobby, I suppose," growled the caretaker. "Here's a blooming fuss about
nothing." He caught up the lamp and went out, leaving us in the dark.

"I picked it up, you know," said Thorndyke, when we were alone.

"I saw you," I answered.

"Good; I applaud your discretion," he rejoined. The caretaker's
supposition was correct. When he returned, he was accompanied by a burly
constable, who saluted us with a cheerful smile and glanced facetiously
round the empty room.

"Our boys," said he, nodding towards the broken window; "they're playful
lads, that they are. You were passing when it happened, sir, I hear."
"Yes," answered Thorndyke; and he gave the constable a brief account of
the occurrence, which the latter listened to, notebook in hand.

"Well," said he when the narrative was concluded, "if those hooligan
boys are going to take to catapults they'll make things lively all
round."

"You ought to run some of 'em in," said the caretaker.

"Run 'em in!" exclaimed the constable in a tone of disgust; "yes! And
then the magistrate will tell 'em to be good boys and give 'em five
shillings out of the poor-box to buy illustrated Testaments. I'd
Testament them, the worthless varmints!"

He rammed his notebook fiercely into his pocket and stalked out of the
room into the street, whither we followed.

"You'll find that bullet or stone when you sweep up the room," he said,
as he turned on to his beat; "and you'd better let us have it. Good
night, sir."

He strolled off towards Henry Street, while Thorndyke and I resumed our
journey southward.

"Why were you so secret about that projectile?" I asked my friend as we
walked up the street.

"Partly to avoid discussion with the caretaker," he replied; "but
principally because I thought it likely that a constable would pass the
house and, seeing the light, come in to make inquiries."

"And then?"

"Then I should have had to hand over the object to him."

"And why not? Is the object a specially interesting one?"

"It is highly interesting to me at the present moment," replied
Thorndyke, with a chuckle, "because I have not examined it. I have a
theory as to its nature, which theory I should like to test before
taking the police into my confidence."

"Are you going to take me into your confidence?" I asked.

"When we get home, if you are