"Quite right."
"Now, then, put yourself in young Starberth's place. You're sitting at this table, where he sat, with your bicycle-lamp beside you; as nervous as he was, or as cool as you might be — either way — Got it? Got the scene?
"Perfectly, thank you."
"For whatever purpose, you get up to go over to that door, which hasn't been opened in God knows how many years; you're not only trying to open a sealed door, but you're going out on a balcony that's blacker than pitch…. What do you do?"
"Why, I pick up the lamp and I — "
"Precisely. That's it. That's the whole story. You hold your lamp while you're opening the door, and flash it out on the balcony to see where you're going, before you've even set foot out there…. Well, that's precisely what our victim didn't do. If so much as a crack of light had shown through this door anywhere, we should have seen it from my garden. But we didn't."
There was a silence. Sir Benjamin pushed his hat over to one side of his head and scowled.
"By Jove!" he muttered, "that sounds reasonable, you know. Still- Oh, look here! There's something wrong. I don't see any earthly way a murderer could have come in this room without an outcry on Starbeth's part."
"Neither do I," said Dr. Fell. "If that encourages you any. I…" He broke off, a startled expression coming into his eyes as he stared at the iron door to the balcony. "O Lord! O Bacchus. O my ancient hat. This won't do."
He went stumping over to the door. First he knelt down and examined the dusty, gritty floor, where bits of dirt and stone had fallen when the door was opened. He ran his hand along them. Rising, he examined the outer face of the door; then he pushed it partly shut and looked at the keyhole.