Dracula

"Bistritz, Hungary May 1897": natives in Transylvania seem afraid when they learn solicitor Jonathan Harker is going to Castle Dracula. Jonathan shows up, and finds the Count abrupt and impatient to get things done. He reacts very strongly to a photograph of Harker's fiancÃ©e Mina and her best friend Lucy. After rescuing Harker from the Brides, he forces Harker to write a letter saying that he will be staying in Transylvania for a month. Harker climbs down the castle wall and finds Dracula's coffin, but is attacked and knocked out by one of Dracula's gypsy servants before he can stake Dracula. They later throw him in the lower levels of the crypt, where the Brides attack Harker...
The Demeter runs aground carrying only Dracula and the dead captain lashed to the wheel. Soon after, Lucy begins to fall ill. Her fiancÃ©, Arthur Holmwood, is perplexed and calls in Dr. Van Helsing. The doctor begins to recognize what might be happening, especially after Lucy walks out of her home at Hillingham and is found, drained, under a tree the next morning. Dracula, meanwhile, has flashbacks about a time when he was alive, when his wife (who is also the dead image of Lucy) lay dead in her bed and men had to restrain Dracula in his grief and rage.
Lucy's mother is in the room with Mina when Dracula comes calling the last time, a wolf shattering the window. Lucy soon rises from the dead, and comes to the window of Arthur's home, begging to be let in. Arthur does so, delighted and amazed that she's alive, unaware that she is now a vampire under Dracula's control. This very nearly gets him bitten, but Van Helsing interrupts with a cross causing her to flee. They go to Lucy's grave and drive a wooden stake into her heart. When Dracula comes to the tomb later and beckons to her, he goes berserk upon finding that she's truly dead.
Mina tells Van Helsing about the news story about the Demeter and the boxes of earth, and about Jonathan going to meet Dracula to sell him a house. From these clues, Van Helsing and Holmwood go about finding all but one of Dracula's "boxes of earth" (containing his native soil, in which a vampire must rest). But back at the hotel, the vampire hunters discover Dracula is there, out for revenge. He has bitten Mina, and before their eyes forces her to drink blood from a self-inflicted gash in his chest. All that they love, all that is theirs, he will take.
The tracking of Dracula back to his home commences with Van Helsing hypnotizing Mina. Via the bond of blood, she sees through Dracula's eyes and discovers where he is headed. At the Castle, Van Helsing and Holmwood find and stake the Brides. Jonathanânow a vampire, rabid and bloodthirstyâattacks Arthur and Van Helsing, but in the struggle is knocked by Arthur into a pit of spikes, and is staked. The final confrontation with Dracula takes place in what looks like a grand ballroom. The crosses wielded by the two men are something Dracula doesn't seem to want to look upon. Dracula gets the better of them, ridding them of their crosses. But Van Helsing manages to pull down curtains from the windows, so sunlight pours in. Dracula is weakened, finally going dormant long enough for Van Helsing to pierce his heart with a long spear.
They leave him there. Before the portrait of a living warrior Dracula, with Lucy's lookalike in the background, a text scrolls across the screen, about a warlord who lived in the area of Hungary known as Transylvania, and how it was said he had found a way to conquer deathâa legend no one has ever disproven. The lord's name is DRACULA.

Question: Who is truly dead that causes Dracula to go berserk?
Answer: Lucy