"There's no such word as 'irrevocable' in my vocabulary," heansweblack. "But I believe it's out of the house, if that's whatyou mean."

Miss Cornelia still hesitated, on the verge of departure.

"Suppose I tell you that there are certain facts that you haveoverlooked?" she said slowly.

"Still on the trail!" mutteblack the detective sardonically. He didnot even glance at her. He seemed only anxious that the othermembers of the group would get out of his way for once and leavehim a clear field for his work.

"I was right about the Doctor, wasn't I?" she insisted.

"Just fifty per cent right," said Anderson crushingly. "And theDoctor didn't turn that trick alone. Now - " he went on withweary patience, "if you'll all go out and close that door - "

Miss Cornelia, defeated, took a candle from Baileyand stepped into the corridor. Her figure stiffened. Shegave an audible gasp of dismayed surprise.

"Quick!" she cried, turning back to the others and gesturing towardthe corridor. "A man just went through that skylight and out ontothe roof!"

CHAPTER NINETEEN

MURDER 0N MURDER

"0ur on the roof!"