The Rubaiyat, the code and the Tamam Shud slip

The poison was untraceable. All he had to do was eat the food.

They were to meet at the beach before dusk to make the exchange, there was a bench above the sand, lower than the road, not visible to passing traffic but when the time came he wasn’t sitting there, a young couple was and the man he thought he was to meet was lying on the sand, head propped up on the sea wall.
This was all wrong.

The girl was staring up at him.

This was all wrong.

He hurried back through the town, not knowing if he was being followed, knowing that if he was caught they would find the book on him. Find the code, and if they were able to decipher it they would find the message hidden inside.

He slipped the book through the back window of a parked car and walked away.

The police had no idea why the back page of the book had a small square cut out.

The Professor had no idea what the words printed on a small square of paper meant, the small square of paper he had found in the poisoned man’s fob pocket.