had mr.nuttel really seen a ghost ? explain in detail.

 No, he did not see a ghost. Vera is just so descriptive in her story account that when he sees men returning from the forest, he interprets them within the context of Vera's vivid tale. It is also important to remember that Mr. Nuttal already was suffering from nerves and anxiety issues. His fragile mental state is why he came to the countryside in the first place. 

Vera had made up atall tale just to trick mr nuttel and he on seeing the three men return covered with mud upto toe shuddered with fear as he had been told that they died three years ago no sooner had he seen the trio enteringvtue house through the open window he quickly retreated out of the house as if he had seen a ghost.