Mr. Chartwell, also known as Black Pat, has been psychologically torturing Winston Churchill for a long, long time. In fact, Churchill has been suffering from depression ever since Black Pat came into his life. Black Pat is a big, menacing, black, smelly dog with a dark side. Only those haunted by him can see him.
Esther Hammerhans is a librarian and a recent widow who decides to rent out her late husband's study. When Mr. Chartwell arrives to ask about the room, a frightened Esther tries to get out of renting it to him. Black Pat, always the conniver, offers her a great sum of money to stay for just a short time and Esther agrees. Will she fall victim to his darkness?