Why does Framton run off without saying good-bye? He is afraid of dogs. He must rush to the doctors. He is angry with the child. He thinks he sees ghosts.

Frantic ran off without saying goodbye because he is afraid of dogs since a pack of dogs cornered him into a cemetery and made him spend the night.

What a ninny?! He doesn't even both to check the facts. He just believes what he is told.

He believes the child without any question. I suppose we are to believe that he had such a terrible nervous condition that he could not check anything. He just had to run to get away.

He is not going anywhere (like to see the doctors). He's just running away.

He probably is afraid of dogs and bugs and germs and snakes and ... you name it and he's likely afraid of it.

The actual answer I think is that he is running away from the "ghosts."