He paused, thinking it out.

“Only they slipped up in one place.  Dick Fleming leased the house to you and they couldn’t get it back.”

“Then you are sure,” said Miss Cornelia quickly, “that tonight Courtleigh Fleming broke in, with the Doctor’s assistance—­and that he killed Dick, his own nephew, from the staircase?”

“Aren’t you?” asked Bailey surprised.  The more he thought of it the less clearly could he visualize it any other way.

Miss Cornelia shook her head decidedly.

“No.”

Bailey thought her merely obstinate—­unwilling to give up, for pride’s sake, her own pet theory of the activities of the Bat.

“Wells tried to get out of the house tonight with that blue-print.  Why?  Because he knew the moment we got it, we’d come up here—­and Fleming was here.”

“Perfectly true,” nodded Miss Cornelia.  “And then?”

“Old Fleming killed Dick and Wells killed Fleming,” said Bailey succinctly.  “You can’t get away from it!”

But Miss Cornelia still shook her head.  The explanation was too mechanical.  It laid too little emphasis on the characters of those most concerned.

“No,” she said.  “No.  The Doctor isn’t a murderer.  He’s as puzzled as we are about some things.  He and Courtleigh Fleming were working together—­but remember this—­Doctor Wells was locked in the living-room with us.  He’d been trying to get up the stairs all evening and failed every time.”

But Bailey was as convinced of the truth of his theory as she of hers.

“He was here ten minutes ago—­locked in this room,” he said with a glance at the ladder up which the doctor had ascended.

“I’ll grant you that,” said Miss Cornelia.  “But—­” She thought back swiftly.  “But at the same time an Unknown Masked Man was locked in that mantel-room with Dale.  The Doctor put out the candle when you opened that Hidden Room.  Why?  Because he thought Courtleigh Fleming was hiding there!” Now the missing pieces of her puzzle were falling into their places with a vengeance.  “But at this moment,” she continued, “the Doctor believes that Fleming has made his escape!  No—­we haven’t solved the mystery yet.  There’s another element—­an unknown element,” her eyes rested for a moment upon the Unknown, “and that element is—­the Bat!”

She paused, impressively.  The others stared at her—­no longer able to deny the sinister plausibility of her theory.  But this new tangling of the mystery, just when the black threads seemed raveled out at last, was almost too much for Dale.

“Oh, call the detective!” she stammered, on the verge of hysterical tears.  “Let’s get through with this thing!  I can’t bear any more!”

But Miss Cornelia did not even hear her.  Her mind, strung now to concert pitch, had harked back to the point it had reached some time ago, and which all the recent distractions had momentarily obliterated.