The greatest puzzle is simple enough when you know the answer.  
Bowser the Hound.
There were just two people to whom the disappearance of that fat hen Reddy Fox had hidden in the hollow stump was not a mystery. One of them was Blacky the Crow. When the farmer and Bowser the Hound had rushed out at the sound of Blacky's excited cawing, Blacky had flown to the top of a tall tree from which he could see all that went on. Everything had happened just as Blacky had hoped it would. Bowser had taken the trail of Reddy Fox, and Blacky felt sure that sooner or later Reddy would lead him back home to Farmer Brown's.
 
Blacky was doubly pleased with himself. He was pleased to think that he had found a way of getting Bowser back home, and he was quite as much pleased because he had been smart enough to outwit Reddy Fox. He didn't wish Reddy any harm, and he felt sure that no harm would come to him. He didn't even wish him to lose that dinner Reddy had come so far to get, but he didn't care if Reddy did lose it, if only his plan worked out as he hoped it would.
 
"I wonder what he'll do with that fat hen," muttered Blacky, as he watched Reddy race away with it thrown over his shoulders. "He can't carry that hen far and keep out of the way of Bowser. I think I'll follow and see what he does with it."
 
So Blacky followed, and his ey............