“I’m quite sure,” he began, “that you all realise why we have asked you to meet us here. It is, of course, in order to enlist your help. We are faced with a difficult problem in this case and feel that a reconstruction of the operation may go far towards clearing any suspicion of guilt from innocent individuals. As you know, Sir Derek O’Callaghan died from hyoscine poisoning. He was a man with many political enemies, and from the outset the affair has been a complicated and bewildering problem. The fact that he, in the course of the operation, was given a legitimate injection of hyoscine has added to the complications. I am sure you are all as anxious as we are to clear up this aspect of the case. I ask you to look upon the reconstruction as an opportunity to free yourselves of any imputation of guilt. As a medium in detection the reconstruction has much to commend it. The chief argument against it is that sometimes innocent persons are moved, through nervousness or other motives, to defeat the whole object of the thing by changing the original circumstances. Under the shadow of tragedy it is not unusual for innocent individuals to imagine that the police suspect them. I am sure that you are not likely to do anything so foolish as this. I am sure you realise that this is an opportunity, not a trap. Let me beg you to repeat as closely as you can your actions during the operation on the deceased. If you do this, there is not the faintest cause for alarm.” He looked at his watch.

“Now then,” he said. “You are to imagine that time has gone back seven days. It is twenty-five minutes to four on the afternoon of Thursday, February 4th. Sir Derek O’Callaghan is upstairs in his room, awaiting his operation. Matron, when you get word will you and the nurses who are to help you begin your preparations in the anteroom and the theatre? Any dialogue you remember you will please repeat. Inspector Fox will be in the anteroom and Inspector Boys in the theatre. Please treat them as pieces of sterile machinery.” He allowed himself a faint smile and turned to Phillips and Nurse Graham, the special.

“We’ll go upstairs.”

They went up to the next landing. Outside the door of the first room Alleyn turned to the others. Phillips was very white, but quite composed. Little Nurse Graham looked unhappy, but sensibly determined.

“Now, nurse, we’ll go in. If you’ll just wait a moment, sir. Actually you are just coming upstairs.”

“I see,” said Phillips.

Alleyn swung open the door and followed Nurse Graham into the bedroom.