A man leaves a £50 note on his desk and leaves work.
When he returns the money is gone.
He has three suspects: the cook, the cleaning lady, and the post man. The cook says he put the money under a book on his desk to keep it safe.
They check and it is no longer there.
The maid says she moved it when she was cleaning to the inside of the book between page 1 and 2.
They open the book and look between page number 1 and 2 but it isn’t there.
The post man says he saw it sticking out of the book and to keep it safe he moved it to between page number 2 and 3.
Once they are done the culprit is promptly arrested.
Who did it and how did he know?