"AFTER NASEBY LEFT the King's Road," said Alleyn, when they were in the car, "Thompson watched Props in the telephone-box. He put two calls through. As soon as he had gone Thompson went in and asked for the numbers. The operator had lost them. Thompson darted out and managed to pick Props up again. He spent the time wandering about the streets, but always drawing nearer this part of the world. Just before Thompson rang up, Props had led him into the jumble of streets round the back of the Unicorn. He kept him in sight until he turned up a cul-de-sac called Simon's Alley. Thompson followed and came to a gate leading into a yard. He looked round and decided that he was somewhere at the back of the theatre. He climbed the gate and found an open window that he believes gives into some part of the Unicorn. It was pitch-dark inside. Thompson was in a quandary. He decided to call me. First of all he managed to find one of our men and told him what he'd seen. That took some time. The man hailed a constable and left him in his place while he himself came round to the gate. That took longer. Thompson, whom Allah preserve, for I won't, prowled round on a Cook's tour in search of a telephone and finally rang me up. Lord knows how long the gate was left unguarded. Quite five minutes, I should say, if not longer."

"Well, sir, whatever Props was up to it would probably take longer than that."

"Yes. Of course it was difficult for Thompson. He didn't want to start blowing his whistle and the gaff at the same time. Now here's where we get out and grope for Simon's Alley. I'll just see the others first."

They left the car and went back a little way to where a second police car was drawn up. Alleyn gave instructions to the six constables who were in it. They were to split up singly, go to the several doors of the theatre, and enter it, leaving the men already on guard in their places.

"I don't know what we'll find," said Alleyn, "but I expect it'll be in the stage half of the theatre. You four come quietly through the stalls, from the several doors, and wait by the orchestra well. Don't use your torches unless you've got to. You come in at the back entrance, and at the stage door. Don't make a move until you get the word from Inspector Fox or myself. If you meet anything, grab it. Right?"

"Right, sir."

"Away you go then. Come on, Fox."

They had pulled up some little way from the back of the Unicorn. Alleyn led the way through a confused jumble of by-streets into the dingy thoroughfare behind the theatre. At last they came into a very narrow, blind street. Alleyn pointed up at the corner building and Fox read the notice: "Simon's Alley."