The question was, by whom and for whom it had been written.
Afternoon school was just over, and the three friends were standing warming their feet on a hot-water pipe, discussing the likelihood of making any other discoveries which might tend to throw more light on the subject, when suddenly a happy thought entered the head of Jack Vance.
"Look here, Diggory.

You said you found this note in a crack in the wall under one of the grub-room windows, and that you thought some fellows were using it as a sort of post-office.

Well, have you been there to see if anything's been put there since ?" "No!" cried Diggory.

"Good idea! I'll go now at once." He walked quickly out of the room, and came back a few moments later at a run.
"I've got one!" he exclaimed, in a low, eager tone.

"Don't let any one see; come to my desk." The note this time was very brief:-- ZUGVIGVZFMWVIGSVKZE.
Diggory hastily fished out his double alphabet, wrote down the proper letters as Jack read out those on the paper, and in a few seconds the translation was complete, and read as follows:-- "_After tea under the pav._" The three boys stared at it in silence.
"What does it mean ?" asked Mugford.
"Why," cried Diggory excitedly, "I see.