“Notice,” Mason said, “that only the first twelve letters in the alphabet are employed. Notice that every word contains either a or b, and that a or b, whenever it appears, is either the second or the third letter from the end of the word. That, coupled with the fact that the words have either five or six letters, is absolutely determinative of the whole business. I wonder if Tragg has got it by this time.”
Della Street said, “I don’t get it.”
“Twelve letters,” Mason said. “Good Lord, Della, it fairly hits you in the face.”
“It doesn’t hit me in the face,” Della Street laughed. “It doesn’t hit me anywhere. I miss it altogether.”
Mason pushed back his chair. “I’m going out for fifteen or twenty minutes, Della. Think it over while I’m gone.”
She said, “Ordinarily, I’m a peaceful woman. I’m not given to homicidal mania, but if you arouse my curiosity this way and then try to go out of that door without telling me what the message says, I’m very apt to assault you with a deadly weapon before you get as far as the elevator.”
Mason said, “I don’t know what the message says.”
“I thought you said you did.”
“No. I said the solution was simple. Good Lord, Della, I can’t give you any more clues than that. I’ve virtually told you the whole thing now.”
“You’ll be back in twenty minutes?”