“You saw that letter? Do you recall its general appearance?”

“Yes⁠—more or less.”

“You will recollect, then, that Mrs. Inglethorp wrote a very distinctive hand, and left large clear spaces between her words. But if you look at the date at the top of the letter you will notice that ‘July 17th’ is quite different in this respect. Do you see what I mean?”

“No,” I confessed, “I don’t.”

“You do not see that that letter was not written on the 17th, but on the 7th⁠—the day after Miss Howard’s departure? The ‘1’ was written in before the ‘7’ to turn it into the ‘17th.’ ”

“But why?”