The Scarlet Letters by Ellery Queen

might have slipped it into the pocket of her robe when she opened the envelope. The robe she was wearing has big patch pockets, and they’re usually full of things.”
    â€œAre you up to a little more snoopery, Nikki?”
    Nikki looked at him. “You want me to search for the booklet.”
    â€œIt would help.”
    â€œAll right,” said Nikki.
    â€œLook for a paperback about four inches by seven, and about three eighths of an inch thick.”
    â€œMartha’s hardly likely to leave it lying around. That means I may have to go into her purse … her bureau …”
    Ellery said nothing.
    â€œI wish,” began Nikki, but she bit off the rest of it; and after a moment she said, “Do you really think it’s a–it’s an affair?”
    â€œLooks like it,” said Ellery.
    â€œThursday, 4 P.M. That’s tomorrow afternoon.” Nikki clenched her gloved hands. “Why does she take such a foolish chance? Hasn’t she had enough of Dirk’s jealousy? Why doesn’t she divorce him and then do what she pleases? I’d like to get my hands on that ‘A’–whoever he is!”
    â€œA?” said Ellery.
    â€œThe ‘ A ’ that signed the message, Ellery. I’ve been beating my brains out trying to think of some man she knows whose first name begins with an A , but I can’t come up with anyone but Alex Conn and Arthur Morvyn. And Alex is a fairy and Art Morvyn has been directing Broadway plays for forty years and must be seventy if he’s a day. It can’t be either of them.”
    â€œThe A isn’t the initial of a name, Nikki.”
    â€œIt isn’t?”
    â€œSignatures are almost invariably dropped below the message, on a line to themselves. It’s true this is a short message and the writer might have added his initial on the same line because there’s so little to it. But then he’d probably have separated the m of p.m. from the A by a dash. You told me there was a comma after p.m.”
    â€œThat’s right.”
    â€œThen the A was part of the message, not a sign-off.” Ellery shrugged. “That’s confirmed by inference. The message undoubtedly refers to an appointment. There are two major elements to any meeting–the time and the place. The time is given as tomorrow at four. The likelihood, then, is that the A refers to the place.”
    â€œI’m relieved,” said Nikki dryly. “I thought you were going to say it’s symbolism.”
    â€œSymbolism?”
    â€œA nice scarlet letter A à la Nathaniel Hawthorne. I just don’t know what to make of it, Ellery. It’s so hard to see Martha in the role of Hester Prynne! She’s just not the adulteress type.”
    â€œIs there one?” inquired Ellery. “Anyway, we’ll know soon enough what A stands for. Probably a primitive code. What you’ve got to do tomorrow, Nikki, is tie Dirk in knots for the whole afternoon. Keep him in that apartment if you have to make love to him. If he insists on going out, delay him on some pretext to make sure Martha gets away.”
    â€œWhat are you going to do, Ellery?”
    â€œMake like a private eye and trail Martha to A –wherever A is.”
    â€œSuppose she leaves the house in the morning?”
    â€œWe’ll have to prearrange a code of our own. Do your best to find out about when she intends to leave the apartment. Phone me forty-five minutes before. It doesn’t matter what you say to me when you call. The mere fact that you’re phoning will be my tipoff.”

B …
    Nikki phoned at twenty minutes after eleven Thursday morning. She was phoning, she told Ellery, to call off their “tentative lunch date.” Dirk had his plot pretty well organized and he was starting to dictate manuscript. He planned to work right through the day.
    â€œWonderful,” said Ellery. “Let me talk to him, Nikki.”
    Dirk