“But Rosie alone there with poor Mrs. Ilam!” sighed Pauline.

“Mrs. Ilam can’t do her any harm, at any rate,” said Carpentaria comfortingly.

And with that he commenced a cautious perambulation of the exterior of Ilam’s house, Pauline following him.

“I wish you would go to my sister until I have something to report,” he murmured. “You will take cold, and you will work yourself up into a fever, and do no good to anybody.”

“I shall not work myself up into a fever,” replied Pauline firmly. “I am capable of being just as calm as you are yourself. Let us go at once into the house—let us go to Rosie.”

“What!” expostulated Carpentaria, “and spoil whatever scheme is going on? No, my dear young lady, we have gone so far that we must go a little further. We must catch the schemers red-handed. If we do not, our night’s work will have been wasted.”

The idea of weakly and pusillanimously changing a course of conduct at the very moment when that course promised the most interesting adventures shocked all the artist in him.

They stared blankly at the house, whose form was clearly revealed in the misty moonlight, but none of whose windows showed the slightest glimmer of light. It was an extremely modern tenement, and its architecture was in no way startlingly original; nevertheless, in those moments it seemed to both of them the strangest, the most mysterious, the most insubstantial house that the hand of man had ever raised.

Suddenly Pauline clutched his arm.

“I hear some one walking somewhere in the grounds,” she said.