“I am afraid that I can’t agree. You have no reason to assume that it must be one of us and no one else. But I would like to hear how you think I or anyone else could have walked out of this room leaving it sealed as it was found.”

“That,” Merlini said, “is the simplest answer of all. You walked out, but you didn’t leave the room sealed. You see, it was not found that way!”

I felt as if I were suddenly floating in space.

“But look—” I began.

Merlini ignored me. “The vanishing murderer was a trick. But magic is not, as most people believe, only a matter of gimmicks and trapdoors and mirrors. Its real secret lies deeper than a mere deception of the senses; the magician uses a far more important, more basic weapon—the psychological deception of the mind. Don’t believe everything you see is excellent advice; but there’s a better rule: Don’t believe everything you think.”

“Are you trying to tell me,” I said incredulously, “that this room wasn’t sealed at all? That I just thought it was?”

Merlini kept watching Garrett. “Yes. It’s as simple as that. And there was no visual deception at all. It was, like PK, entirely mental. You saw things exactly as they were, but you didn’t realize that the visual appearance could be interpreted two ways. Let me ask you a question. When you break into a room the door of which has been sealed with paper tape on the inside, do you find yourself still in a sealed room?”

“No,” I said, “of course not. The paper has been torn.”

“And if you break into a room that had been sealed but from which someone has already gone out, tearing the seals—what then?”

“The paper,” I said, “is still torn. The appearance is—”

“—exactly the same!” Merlini finished.

He let that soak in a moment, then continued. “When you saw the taped window, and then the torn paper on the door, you made a false assumption—you jumped naturally, but much too quickly, to a wrong conclusion. We all did. We assumed that it was you who had torn the paper—when you broke in. Actually, it was Dr. Garrett who tore the paper—when he went out!”

Garrett’s voice was a shade less steady now. “You forget that Andrew Drake phoned me—”

Merlini shook his head, “I’m afraid we only have your own statement for that. You overturned the phone and placed Drake’s body near it. Then you walked out, returned to your office where you got rid of the knife—probably a surgical instrument which you couldn’t leave behind because it might have been traced to you.”

Doran, hearing this, whispered a rapid order to the detective stationed at the door.