When you get there after dark there will be no ghost and to find out what type of monster you are dealing with you will have to examine the scorched grass around the well and the burned corpse of the animal.
For The Witcher 3: Wild Hunt on the PlayStation 4, a GameFAQs message board topic titled 'Is the point of no return obvious? (Optional) Find evidence of the spirit's presence using your Witcher Senses.
