Fatty’s hands shook with excitement. He might be able to do something startling now! He must think carefully what to write. The men who used this room were evil, and they used it as a meeting place for evil reasons. They must be stopped. They were evidently in the middle of some big affiair at the moment, and it was up to Fatty to stop them.
He took a rather squashy orange from his pocket. He looked round for a glass. There was one on the shelf. He squeezed his orange into it, then picked up the pen the men had left. The nib was clean and new.
Should he write the visible letter first, or the secret one? Fatty decided on the visible one, because it would be easier then to write the invisible one, as he could see where he had written the first letter.
He began:
“DEAR FIND-OUTERS - I have made a wonderful discovery, most awfully exciting. I can’t leave here, because I am guarding something - but I want to show you what it is. All of you come as soon as you can, and I will let you in when you knock. - Yours,
‘FREDDIE.’ ”
That seemed all right - just what the man had commanded him to write. But the others would smell a rat as soon as they saw the name “Freddie” at the bottom. He always signed himself Fatty in notes like this.
Then he set to work to write the letter in secret ink - or rather in orange juice.
“DEAR FIND-OUTERS” - he wrote - “Don’t take any notice of the visible letter. I’m a prisoner here. There’s some very dirty work going on; I don’t quite know what. Get hold of Inspector Jenks AT ONCE and tell him everything. He’ll know what to do. Don’t come near the place, any of you. - Yours ever,
‘FATTY.’ ”