House of Dark Shadows

House of Dark Shadows is a 1970 American feature-length horror film directed by Dan Curtis, based on his 1966 - 1971 soap opera "Dark Shadows."  In this film expansion, vampire Barnabas Collins (Jonathan Frid) searches for a cure for vampirism so he can marry a woman who resembles his long-lost fiancée Josette (Kathryn Leigh Scott).

Plot
Willie Loomis, the Collins family handyman, is searching for old treasure in the family mausoleum when he accidentally frees Barnabas Collins, a 175-year-old vampire who enslaves him. Upon his release, he attacks Daphne Budd, secretary to Collinwood's matriarch, Elizabeth Collins Stoddard. She is discovered by Jeff Clark, who takes her back to the house where Dr. Julia Hoffman administers medical attention to her.

Barnabas introduces himself to the family under the guise of a "cousin from England". Elizabeth and the others are intrigued by Barnabas and take an instant liking to him. Barnabas insists on moving into the Old House and hosting a ball in honour of the family; however, on the night of the ball, Elizabeth's daughter Carolyn Stoddard is bitten by Barnabas while she is getting ready.

Later on at the ball, he is introduced to young David Collins's governess and Jeff's girlfriend Maggie Evans and is instantly smitten with her, as she bears a striking resemblance to his long-lost fiancée, Josette du Pres. Maggie is thinking about leaving Collinwood, but Barnabas persuades her to stay. Back at the Old House, he tells Willie about Josette and how she took her own life on the night they were to be married. Carolyn overhears and threatens to expose him out of jealousy. Enraged, Barnabas delivers a deadly bite to Carolyn, much to Willie's horror. A shaken Willie takes Carolyn back home; she slowly walks to the doorway, but she is soon discovered slumped in the doorway—dead—by the maid, Mrs. Johnson.

Funeral services are held for Carolyn, and she is buried in the Collins family mausoleum. Dr. Hoffman analyzes samples of Carolyn's blood and recognizes trace elements of the same unknown virus that was present in Daphne Budd's blood sample. Professor T. Eliot Stokes, a friend of the family, confers with Julia and tells her that the recent attacks in Collinsport may have been caused by a vampire.

Carolyn rises as a vampire and almost attacks David. Stokes and Julia try to explain, but Elizabeth and Roger refuse to listen. Carolyn's former fiancé Todd encounters her and she bites him. After he is taken back to Collinwood, the family realize that Stokes and Julia were correct about the vampires. Todd again sneaks out in search of Carolyn, but she is cornered and staked, instantly killing her.

Julia eventually discovers that Barnabas is the vampire responsible. She visits him at the Old House and convinces him that she can use her methods to make him human and he reluctantly agrees. Julia gives him injections which allow him to walk in the daylight. Over time, Barnabas and Maggie begin to spend time together while Jeff is away in Boston. Stokes confronts Julia about helping Barnabas—and realizes she is love with him—and reminds her that he is in love with Maggie. Overcome with jealousy, Julia gives Barnabas an injection which causes him to age rapidly. Out of rage, he strangles her to death. A terrified Maggie witnesses this and tries to flee, but is caught and bitten by Barnabas before she can escape and he vows to come back for her. Jeff soon returns, and he is informed of the family history by Stokes and Roger and that Barnabas intends to make Maggie his bride. That night, Barnabas bites Maggie again, rejuvenating him, and then abducts her.

Jeff and the others pursue them; however, Roger and Stokes are killed. Jeff eventually finds Maggie at an old church in a trance and in Josette's wedding gown. Willie warns him against trying to stop Barnabas and knocks him out. Willie leads Maggie out of the room to where Barnabas is waiting for her. He lays her down on an altar and is about to bite her when Jeff wakes up and shoots at him, but Willie, running to stop Barnabas, moves in the way, and is hit by Jeff's crossbow bolt. Barnabas lures Jeff out of his hiding place and forces him to be a witness by placing him in a trance; however, as Barnabas attempts to bite Maggie, he screams in pain as he's struck in his back. Turning around, he's shocked then enraged to discover that it was Willie—in his final act of redemption—who stabbed him with the crossbow bolt. Barnabas strangles the mortally wounded Willie, but Loomis's attack breaks Jeff out of Barnabas's trance long enough for Jeff to finish driving the bolt through the vampire's back, ultimately bursting through his bloody chest. Maggie, now revived, is rescued by Jeff, both briefly observing the bodies of the presumably dead vampire and Willie Loomis before departing the ruined chapel.

In a post-credits scene, Barnabas's body transforms into a bat and then vanishes.