Patty raged up and down the room, melodramatically clutching at her hair and staring at Nan with her blue eyes. "It is a deep-laid plot, but it shall be foiled by Patricia Sherlock,—the only lady detective in captivity!"
"Patty, do behave yourself! What is the matter with you? You act like a lunatic!"
"I'll tell you, Nan, honey," and Patty suddenly sat down on the couch, among a pile of pillows. "But first read that invitation and see if you see anything unusual or suspicious about it."
"I can hardly read it; for this writing looks like that on the obelisk,—or at least it's nearly as unintelligible. But it seems to say that Mrs. Robert Homer requests the pleasure of your company at luncheon on Tuesday, April the eighth, at half-past one o'clock. Nothing criminal about that, is there?"
"Is there! There is, indeed! Nan, you're the dearest, sweetest, loveliest lady in the whole world, but you can't see a hole through a ladder. So I'll tell you. The date of that party is really April the FIRST. I mean, Marie wrote April the first! And if you'll observe, somebody else has put a twisty line around that ONE and made it into an EIGHT! Why, it's as plain as day!"
"It certainly is, Patty," and Nan looked at the girl in astonishment and admiration. "How did you ever happen to notice it?"
"Why, it just jumped out at me. See, a different pen was used. The line is thicker. And nobody would make an EIGHT that way. They'd make it all with one pen mark. And this is a straight up-and-down ONE, and that rest of it was put on later. And, anyway, Nan, if there were any doubt, don't you see it isn't TH after it as it ought to be for the eight, it's ST?"
"You can't tell which it is in this crazy handwriting," and Nan scrutinised the page.
"Yes, you can," and Patty stared at it. "You wouldn't notice the difference, if you weren't looking for it, but it IS ST. I see it all, Nan! You know Bee didn't want this luncheon, and to get out of it, she changed that date before the invitations were sent! And you see, by the eighth, she'll be back in school!"
"Are both dates Tuesday?" said Nan, thinking.