“It’s possible, of course,” agreed Alleyn, “but look at it for a minute. Suppose Liversidge is the murderer. Liversidge plans to take off the weight. Instead of slipping round, unseen, to the back ladder after the last curtain, which would have been comparatively easy, he goes first to his dressing-room, knowing that he must come out again almost immediately into the brightly-lit narrow passage, where any of the others may be hanging about. Well, he risks that and comes out to find Parsons directly in his way. He knows that Parsons will see him go up to the back of the stage—knows, in short, that he is a man who can hang him. He decides to risk all this on the chance of bribing or corrupting the man. Do you think he’d do it? I don’t. And the same argument applies to Miss Dacres. To all the rest of the cast for that matter. I think when you see Parsons you will agree that he is not a corruptible type. Check his statement by all means, my dear chap, but I feel certain he is speaking the truth. And now let us have a look at the back of the theatre.”

“The back of the theatre, sir?”

“Yes. When I chased round on the trail of Master Palmer, I thought of something that may be of interest. Come across the stage, will you?”

He led the way out of the dressing-room passage to the stage. They had turned on the working-lights, two desolate yellow bulbs up in the dusty proscenium, that cast a little dreary light on the tops of the box-set. Nothing had been moved. The door into the set stood open and through it they could see the white cloth, the chairs pushed back from the table, curiously eloquent, the huddle of broken glass and dead flowers, and the enormous bottle lying on the table.

“That can all be cleared away,” said Wade. “We’ve gone over every inch of it to-day.”

“Come round behind the set,” said Alleyn.

They groped their way round. The stage smelt of old glue and dead paint. Alleyn switched on his torch and led Wade to the back wall.

“Here’s the back ladder up to the grid. That, I feel sure, is the one that was used. Have you tried it for prints?”

“Yes. It’s a fair muck of prints—so far, nothing that’s any good to us. The stage-hands used it over and over again.”

“Of course. Well now, see here.”

In the back wall, a little to the left of the ladder, was a door.

“We noticed this on the plan,” said Alleyn, “and discussed it as a possible entrance for—say Mason.”