Dark Shadows starts when the Collins family establish their port business in Maine and begin a new life there. Years later, Barnabas Collins dismisses the love of their maid Angelique Brouchard because of another woman, Josette du Pres. Angelique resorts to sorcery to take revenge on Barnabas which causes his parents’ death as well as Josette’s. Due to these unfortunate circumstances, Barnabas tries to kill himself but fails to do so. It turns that he has been cursed to become a vampire. Angelique attempts to win his affection but Barnabas still can’t afford to love her. Because of this, Angelique sets Barnabas up, causing people to hunt him down and bury him alive in a coffin.
Almost 200 years later, in the year 1972, Maggie Evans, seeks a job as the Collins’ governess using the name Victoria Winters. She encounters Elizabeth Collins and her nephew David, who claims that his dead mother is still lingering in this world. Victoria also meets the other members of the family including David’s psychiatrist, Julia Hoffman, his father Roger, and Carolyn, Elizabeth’s daughter. On her first night in Collins’ residence, Josette’s ghost appears before her and warns her about the return of a certain person.
Meanwhile, some construction workers accidentally dig up Barnabas’ coffin and sets him free. Barnabas then proceeds to his former home and introduces himself to the Collins as a distant relative.
With Barnabas’ help, Elizabeth gains access to the family’s hidden treasure inside the house. Meanwhile, Hoffman hypnotizes the vampire and unveils his true nature.
Barnabas falls for Victoria because she looks a lot like Josette. He also encounters Angelique again who warns him about meddling with her business. Barnabas then decides to resurrect their family’s cannery business and even usurps some of Angelique’s employees to work for him. Angelique tries to strike a deal with Barnabas but to no avail.
Barnabas plans an event where he can reintroduce the Collins family to the people of Maine. During the party, he learns from Victoria that she is really an escapee from an asylum. Angelique also arrives and gets hurt when she sees Barnabas and Victoria kissing. On the other hand, Barnabas discovers that Hoffman is using his blood to achieve eternal life. He ends up killing the psychiatrist and disposing her body on the bay.
Later on, Barnabas catches Roger as he tries to unlock the secret room. Barnabas makes him choose between money and David but Roger chooses to have lots of money. In the middle of the ballroom, a disco ball falls and Barnabas saves David with his vampire powers. Victoria realizes what Barnabas truly is and she leaves the house right away.
After being dumped again, Angelique encages Barnabas in coffin again and leaves him a mausoleum. Fortunately, David comes to his rescue. However, Angelique puts the blame on Hoffman’s death on Barnabas and the townspeople start going after him and his family.
In the mansion, Angelique and Barnabas engage in a battle. Carolyn joins in, transforming into a werewolf while David’s mother proves to be still existing when she manages to throw off Angelique. At the end, Angelique dies with Barnabas still refusing her love.
From David’s mother’s ghost, Barnabas learns that Victoria is off to kill herself. Barnabas is not able to prevent her from jumping off the cliff but he retrieves her body and transforms her into a vampire. Victoria, now Josette, wakes up and reconciles with Barnabas. The rest of the Collins meanwhile are determined on starting a new life.
The movie ends with Hoffman coming back to life while lying at the bottom of the sea.