Bad Moon (1996)

In this intimate horror thriller, Ted Harrison, an adventurous photojournalist, is transformed after being bitten by a strange beast in Nepal. After his ordeal, his sister welcomes him home, where only the family dog, Thor, recognizes the terrible significance of the man's experience. Ted struggles to retain the last vestige of his humanity before the beast growing within him destroys his unsuspecting sister and her innocent son. As his lust for blood begins to override his sense of conscience, all that stands in his way is Thor. But the monster who was Ted might just underestimate the unshakable bond between a boy and his dog.