Barnabas Collins was born in 1770, as the son of Joshua Collins (Louis Edmonds) and Naomi Collins (Joan Bennett), in Collinsport, Maine. Barnabas developed close ties with his uncle Jeremiah Collins. During the flashback, Barnabas intended to marry an heiress from Martinique named Josette du Pres (Kathryn Leigh Scott), but had a brief affair with Angelique Bouchard (Lara Parker), Josette's maidservant.

Upon Angelique's arrival in Collinsport for the wedding in 1795, Barnabas was determined not to resume his affair. The spurned Angelique Bouchard, a practitioner of witchcraft, used a number of spells to manipulate Barnabas and his family and force his agreement to marry her. Barnabas discovered Angelique's duplicity, and shot her. With what she believed to be her dying words, she took revenge on Barnabas by summoning a vampire bat from hell to attack him. Barnabas fell extremely ill and died. Angelique survived and attempted to rescind the curse, but was unsuccessful.

Barnabas shortly thereafter rose as a vampire, and soon strangled Angelique. Collins later frightened his aunt Abigail (Clarice Blackburn) to death, and left the hatefully fanatic witch-hunter Reverend Trask (Jerry Lacy) entombed alive in the Old House basement. Sarah Collins died of pneumonia after a cold night spent hiding in the woods from her deceased brother. Adding to Barnabas' grief, his mother Naomi committed suicide after discovering his secret. Barnabas Collins blamed Angelique for the deaths of both his sister and his mother, and also blamed Lt. Nathan Forbes (Joel Crothers), who had told Naomi about him. Barnabas strangled Forbes, and attempted to transform Josette into a vampire. Josette was willing, if not fully cognizant of what this would entail, until Angelique revealed a vision of what she would become. Fleeing from Barnabas, Josette leapt off the cliffs of Widow's Hill to her death.

Unable to bear what he had become, Barnabas Collins asked his father, Joshua, to destroy him. Joshua Collins was unable to slay his son, and ordered servant Ben Stokes (Thayer David) to nail a cross to the inside lid of Barnabas' coffin and to wrap chains on its outside, forever imprisoning the vampire in a secret room of the family mausoleum at Eagle's Hill Cemetery.

In 1967, while searching the Collins family crypt for their rumored lost jewels, Willie Loomis (John Karlen) stumbled upon the chained coffin in which Barnabas slept. Believing the coffin to contain the Collins family riches, Willie inadvertently released the vampire. Barnabas attacked Willie and turned him into his unwilling servant.

Barnabas Collins introduced himself to the modern Collins family as a cousin from England, a hard-working businessman never seen during the day. The family accepted this story, despite having never before heard of him, because of his resemblance to the portrait of the ancestral Barnabas which hung in Collinwood. The thirsty Barnabas made victims of several Collinsport residents. He was particularly taken with waitress Maggie Evans (Kathryn Leigh Scott), who resembled his long-lost love, Josette. Barnabas was told by David Collins (David Henesy) that Josette's spirit still haunted the Collinwood estate, where it periodically helped and protected others, including young David. Barnabas Collins kidnapped Maggie, hypnotized her to believe that she was Josette, and planned to make her his vampire bride. Maggie escaped with help from the ghost of Sarah Collins, but the emotional distress of being kidnapped caused Maggie to regress to a childlike mentality and to forget all that had happened. Barnabas Collins then targeted David's governess, Victoria Winters (Alexandra Moltke) as a potential consort. He tried to seduce her away from her fiancé Burke Devlin (Anthony George), and then to bite her. The ghost of Sarah appeared repeatedly throughout and warned Barnabas, who was tormented by a feeling of responsibility for her death, away from evil deeds.

Maggie was sent to Wyndcliff Sanitarium, where Dr. Julia Hoffman (Grayson Hall) tried to get her to remember what happened and to identify her kidnapper. Dr. Hoffman found that the answer lay somewhere at Collinwood, and discovered who and what Barnabas was. Julia fell in love with Barnabas and attempted to cure him, and hypnotized Maggie to forget everything Barnabas had tried to do to her. Barnabas Collins initially distrusted Julia, and when her medical cure failed, viewed her as a risk who would be able to expose his true nature. He attempted to kill Julia, or to drive her mad so that no one would believe her accusations. Ultimately, Barnabas came to see Julia as a useful ally. The romantic relationship Julia desired never happened on-screen, but she became Barnabas' chief confidante and helped him many times, while Barnabas Collins became genuinely devoted to Julia and would go to extraordinary lengths to protect or rescue her when she ran afoul of enemies such as Angelique (eventually a firm friend), ghosts, and the ancient Leviathans.

Barnabas Collins's great love was his fiancée from 1795, Josette du Pres, but throughout the show he had interest in many different women, including Maggie Evans, Victoria Winters and Roxanne Drew. He wanted these women to share his vampire existence, and wanted Maggie and Victoria to assume the identity of Josette. His closest ally and friend was Dr. Julia Hoffman, who was quietly in love with him and supported his attempts to find happiness. While aware that Julia did have strong feelings for him, Barnabas' complex feelings for Julia evolved from initial fear and distrust to deep affection, devotion and protection. At one point, Barnabas Collins admitted to Willie Loomis that he cared for Julia more than he appeared to.

The 1970 MGM film House of Dark Shadows centers on the release of Barnabas Collins from his coffin by Willie Loomis. Unlike Frid's television portrayal of Barnabas, the Barnabas featured in the film was truer to a typical evil vampire, who by the end of the film had killed half of the Collins family. Barnabas himself is killed by Jeff Clark, now depicted as Maggie's boyfriend, and a dying Willie Loomis, when Barnabas tries to make Maggie Evans his vampire bride. Barnabas does not appear in the sequel, Night of Dark Shadows, which focuses on another relation, Quentin Collins.

In the 2012 film Dark Shadows, Barnabas is played by Johnny Depp as a somewhat-modernized version of the character from the original series. He has a deep obsession with Josette, has no forgiveness for those who betray him, and believes that his curse can be reversed. He shows deep emotions for his modern family members, whose lives he longs to be part of. He displays his television counterpart's powers and abilities, while subject to his cold vampire instincts. Barnabas tries to win the love of David's governess Maggie Evans, now called Victoria Winters, who reminds him of his lost beloved Josette. Depp's version is up to date with popular culture and has a strong taste for rock music. He wears a hair and clothing style similar to his late 1960s counterpart, but dresses more colorfully. His character is portrayed as somewhat more sexually active and eccentric than before. This incarnation has a different relationship with Dr. Hoffman, who never becomes his ally.

Barnabas often blamed his moments of cruelty on his transformation into one of the undead or "nosferatu," but other characters revealed that Barnabas was not always the reluctant victim that he claimed. He carried on a sexual dalliance with the obsessed Angelique despite his claim of love for Josette, which set in motion many tragedies in his life. Jealousy and wounded male pride caused him to fatally wound his uncle in a duel, after Jeremiah's elopement with Josette. He attempted to back out of his agreement to marry Angelique after she cured his sister of illness. Given proof that his newlywed bride Angelique was a witch, he attempted to murder her. A drunken Ben Stokes admitted that Barnabas, prior to his change, "... weren't no good then, neither — but now, he's worse!" When the vampire tried to silence his own father by killing him, an astonished Joshua Collins exclaimed: "You would kill even me! You must have always had so much hatred in you. No one could be filled with it so quickly!" While many of his flip-flopping infatuations with nubile young women could be attributed to his vampire curse and his need to find a vampire bride, his romantic choices during his periods as a human were equally immature and baffling. In later interviews, Jonathan Frid admitted this was all part of the character's success, "... the lies he told to himself."

However harsh or impulsive he may have been, Barnabas is nevertheless not without a conscience, either as a human or as a vampire. He is shown to be capable of feeling guilt for wrongs committed, as well as love for other people. For example, he shows a softer side for Dr. Julia Hoffman as he becomes closer to her, and once mentioned that he cared for her more than he let on. He risked his life whenever she was in grave trouble, and only when the Leviathans gave the order to have Julia killed did Barnabas have the strength to break free of their control. When Angelique tried to endanger Julia's life, an enraged Barnabas warned her that if she ever tried to harm Julia again, he would personally see to her own destruction. His confrontation with Angelique over the deaths that his curse had caused revealed that he did care deeply for his mother, his sister and for Josette.

Barnabas' abilities mimic those of the classic vampire Dracula, and include immortality, superhuman strength, superhuman speed, hypnotism, shape-shifting and teleportation. However, Barnabas has also been known to use sorcery. In an early storyline, he attempted to drive Julia mad by conjuring the spirit of her dead colleague, Dave Woodard. In 1795, Barnabas briefly resurrected Josette DuPres, who in the 20th century would warn the Collins family of approaching danger while wandering the Collinwood halls, and he used visions to lure Rev. Trask into a fatal trap. These seemingly magical abilities were never explained, but made Barnabas a deadly protagonist.

Jonathan Frid first appeared as Barnabas Collins in 1967 in episode #211, but Collins' hand was briefly seen in the climax to episode #210, prior to Frid's introduction. Series regular Timothy Gordon (uncredited) provided the hand, which was first seen choking Willie Loomis.

In a 1971 TV Guide article, Dark Shadows head-writer Sam Hall discussed the outline the show's finale would have taken had it not been canceled sooner than anticipated. Among other things, the plans involved Barnabas, a vampire once again, becoming mysteriously ill. Julia, deducing that his illness was due to his unique connection to Adam, would travel to Singapore to treat Adam, and there fall seriously ill herself. The now-recovered Barnabas would come to her and, at long last, declare his love and ask her to become his wife. Knowing that Angelique would never allow Julia to live, they would remain in the Far East after their marriage, and Julia would permanently cure Barnabas of his vampirism.

• Josette du Pres; fiancee
• Angelique Bouchard Collins; rival, later wife
• Victoria Winters; romantic interest
• Maggie Evans; romantic interest
• Sarah Collins; younger sister
• Roxanne Drew; romantic interest
• Dr. Julia Hoffman; confidante
• Quentin Collins; distant cousin
• Willie Loomis; human slave and daytime protector

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