“The fact that the murderer could not enter until 9:30 or thereabouts explains why the torn edges of LL32 Left and LL30 Left did not coincide. It was necessary for Field and Barry, you see, to come in at different times. Field could not very well enter with Barry or even at a noticeably late hour—the matter of secrecy was too important to Barry, and Field understood, or thought he did, how necessary it was for him to play the secret game. “When we pinned the guilt on Barry Thursday night, we resolved to question subtly the other members of the cast as well as workmen backstage. We wanted to find out, of course, whether any one had actually seen Barry leave or return. As it happened, no one had. Everybody was busy either acting, redressing, or working backstage. We conducted this little investigation after the performance that night, when Barry had already left the theatre. And it was checkmate, right enough. “We had already borrowed a seating-plan from Panzer. This map, together with the examination of the alleyway on the left and the dressing-room arrangement backstage—an examination made directly after the second act Thursday night—showed us how the murder was committed.” Sampson stirred. “I’ve been puzzling my wits about that,” he confessed. “After all, Field was no babe-in-the-woods. This Barry must be a wizard, Q. How did he do it?” “Every riddle is simple when you know the answer,” retorted the Inspector. “Barry, whose freedom began at 9:20, immediately returned to his dressing-room, slapped on a quick but thorough facial disguise, donned an evening-cloak and the tophat which was part of his costume— you’ll remember he was already dressed in evening-clothes—and slipped out of his room into the alley. “Of course you can’t be expected to know the topography of the theatre. There is a series of tiers in a wing of the building backstage, facing the left alley, which is made up of dressing-rooms. Barry’s room is on the lowest tier, the door opening into the alleyway. There is a flight of iron steps leading down to the pavement.