“I am not,” Arnold answered.  “I am a friend of his niece here, Miss Ruth Lalonde.  I know very little of Isaac, although I see him here sometimes.”

“I should like to know your name, if you have no objection,” the inspector remarked.

“My name is Chetwode,” Arnold told him.  “I occupy a room on the other side of the passage.”

“When did you last see Isaac Lalonde?”

Arnold did not hesitate for a moment.  What he had seen at Hampstead belonged to himself.  He deliberately wiped out the memory of it from his thoughts.

“On Thursday evening here.”

The inspector made a note in his pocket-book.  Then he turned again to Ruth.

“You can give me no explanation, then, as to your uncle’s absence to-night?”

“None at all.  I can only say what I told you before—­that I expected to find him here on my return.”

“Was he here when you left this morning?”

“I believe so,” Ruth assured him.  “He very seldom comes out of his room until the middle of the day, and he does not like my going to him there.  As we started very early, I did not disturb him.”

“Have you any objection,” the inspector asked, “to telling me where you have spent the whole of to-day?”

“Not the slightest,” Arnold interposed.  “We have been to Bourne End, and to a village in the neighborhood.”

The inspector nodded thoughtfully.  Ruth leaned a little forward in her chair.  Her voice trembled with anxiety.

“Please tell me,” she begged, “what is the charge against my uncle?”

The inspector glanced over his shoulder at that inner room, from which fitful gleams of light still came.  He looked down at the heap of pistols and ammunition by his side.

“The charge,” he said slowly, “is of a somewhat serious nature.”

Ruth was twisting up her glove in her hand.

“I do not believe,” she declared, “that Isaac has ever done anything really wrong.  He is a terrible socialist, and he is always railing at the rich, but I do not believe that he would hurt any one.”

The inspector looked grimly at the little pile of firearms.

“A pretty sort of armory, this,” he remarked, “for a peace-loving man.  What do you suppose he keeps them here for, in his room?  What do you suppose—­”

They all three heard it at the same time.  The inspector broke off in the middle of his sentence.  Ruth, shrinking in her chair, turned her head fearfully towards the door, which still stood half open.  Arnold was looking breathlessly in the same direction.  Faintly, but very distinctly, they heard the patter of footsteps climbing the stone stairs.  It sounded as though a man were walking upon tiptoe, yet dragging his feet wearily.  The inspector held up his hand, and his subordinate, who had been searching the inner room, came stealthily out.  Ruth, obeying her first impulse, opened her lips to shriek.  The inspector leaned forward and his hand suddenly closed over her mouth.  He looked towards Arnold, who was suffering from a moment’s indecision.