“Can you see invisible ink?” asked Bets. “I shouldn’t have thought you could.”
The others laughed. “Silly! The ink isn’t invisible - it’s only the writing you do with it that is.”
“I’ve got a bottle,” said Fatty. “It’s very expensive.”
He took a bottle from his pocket. It was quite small, and contained a colourless liquid which, to Bets, looked like water.
Fatty took out his note-book and a pen with a clean new nib. He put the bottle on the table, and undid the screw-top.
“Now I’ll write a secret letter,” he said, “and my writing will be invisible.”
Bets leaned over him to see. She lost her balance and jerked hard against the table. The bottle of invisible ink was jolted over, rolled to the edge of the table, and neatly emptied its contents on the floor in a small round puddle, near Buster.
“Woof!” said Buster in surprise, and began to lick it up. But the taste was horrid. He stopped and looked up at the alarmed children, his pink tongue hanging out.
“Oh, Buster! Buster, you’ve drunk invisible ink!” cried Bets, almost in tears. “Fatty, will he become invisible?”
“No, idiot,” said Fatty. “Well, that’s the end of the ink. What a clumsy you are Bets!”