In New York City, struggling artist Evelyn “Evie” Jackson makes a living freelancing for a catering business with her best friend Grace. Evie takes a DNA test, discovering she has a distant cousin in England named Oliver Alexander. She meets Oliver, who tells her the scandal of her great-grandmother, Emmaline, who had a secret child with a black footman. He invites her to an upcoming family wedding in England. Evie arrives in Whitby at the New Carfax Abbey, where she meets the lord of the manor, Walter De Ville, and Mrs. Swift, a longtime maid of the estate. She also meets the rest of the Alexander family and the maids of honor, friendly Lucy and condescending Viktoria.

Evie gradually begins to notice unsettling occurrences during her stay. She sees an apparition of Emmaline, who was shown in a flashback, hanging herself from the staircase. Maids start disappearing as they are attacked by a shadowy figure. Evie finds herself romanced by De Ville before discovering he had been researching her before her arrival. She confronts him and threatens to leave, but the two reconcile and have sex.

The family hosts a rehearsal dinner, where Evie expects to finally meet the bride and groom. Instead, De Ville announces that he and Evie are to be wed. The butler, Mr. Field, slits a maid’s throat and pours her blood into a bowl. De Ville, Lucy, and Viktoria are all revealed to be vampires who then drink the maid’s blood. Evie’s ancestors, the Alexanders, are one of the three families who, for centuries, have each offered one of their women to become De Ville’s wife in exchange for protection and wealth. Emmaline was originally intended to be De Ville’s third bride, but she killed herself due to her guilt of killing humans, and due to the loss of her love, Evie’s great-grandfather, and infant son. The Alexander family had trouble finding a female member until they found Evie. Viktoria locks a frantic Evie inside a coffin, but she is freed by Mrs. Swift, who is killed by Mr. Field. Evie makes it into town and asks an elderly couple, who reveal themselves to be Jonathan and Mina Harker, for help but is knocked unconscious, as they work for De Ville.

Evie wakes up to find herself with one of the maids, Imogen, and De Ville. De Ville reveals himself to be Dracula as he mentions he was once known as the “Son of the Dragon”. Evie then watches De Ville bite into Imogen’s leg and falls unconscious. Upon waking up, Evie is now in a wedding dress, walking down the aisle to wed De Ville. As they finish exchanging vows, she bites De Ville’s arm, consuming his blood, and instantly transforms into a vampire. She sets the wedding chapel on fire, stabs De Ville in the heart, which rapidly ages him, and flees with Diya, another maid. An enraged Viktoria ambushes Evie, who is helped by Diya. After Diya flees, Viktoria attacks Evie again before Lucy intervenes. The two vampires fight before Lucy impales both Viktoria and herself on a spear, turning them both into ashes.

Shortly thereafter, Evie is attacked by Field wielding a spear, who states that he wished he had killed her great-grandfather and grandfather, before she kills him by breaking off the spearhead and stabbing him in the chest. She is then chased by a wall-crawling De Ville, who grabs her by the throat. She breaks free by severing his wrist with a cutting wire and kicks him into the flames. As he burns alive, she loses her powers due to his death and reverts into the human form. Evie escapes as the manor is engulfed in flames.

Two weeks later, in London, Evie and Grace have tracked down Oliver, who prepares to flee after having paid off the police. The two women intend to kill him for tricking Evie and being complicit in the murders committed by the vampires.