What is the main conflict in Don't Look Now by Daphne du Maurier?

"Don't Look Now," published in 1970, is a tale of the supernatural involving a British couple vacationing in Venice to escape the pain of their young daughter's recent death. An encounter with two sisters at a cafe, and the blind one's claim that she can "see" the deceased child sitting with her parents, launches a series of events that ends violently. The story was made into a suspense movie a few years after it was published and has remained one of du Maurier's best-known tales.