Half Light (2006) on Netflix

In London, the successful novelist Rachel Carlson is married with the mediocre aspirant writer and great editor Brian and they live in a comfortable apartment with her son Thomas Carlson. While writing a new novel, Rachel forgets the back gate open and Thomas drowns in a lake. Eight months later, Rachel is still disturbed and she decides to move alone to a seaside cottage in Ingonish Cove, a very small coastal Scottish village. Sarah decides to visit the lighthouse in the island close to her house to help in her research for the book, where she meets the lighthouse keeper Angus McCulloch. One month later, she falls for him and they make love. On the next morning, she invites Angus to go to a birthday party in the shore, and while waiting for him, she discloses that Angus McCulloch died seven years ago. Rachel returns to the island trying to prove her sanity to her neighbor Finlay Murray, and they see that the lighthouse is completely empty. Rachel has a breakdown and she asks for help to her psychiatric Dr. Robert Freedman and to best friend Sharon Winton while she is haunted by ghosts.