Vampire in Brooklyn

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An abandoned ship crashes into a dockyard in Brooklyn, New York, and the ship inspector, Silas Green, finds it full of corpses. Elsewhere, Julius Jones, Silas's nephew, has a run-in with some Italian mobsters. Just as the two goons are about to kill Julius, Maximillian, a suave, mysterious vampire (who arrived on the ship in his intricately carved coffin), intervenes and kills them. Soon after, Maximillian infects Julius with his vampiric blood, before Julius turning into a decaying ghoul and claiming that it has benefits; he then explains that he has come to Brooklyn in search of the Dhampir daughter of a vampire from his native Caribbean island in order to live beyond the night of the next full moon.
This Dhampir turns out to be NYPD Detective Rita Veder, who is still dealing with the death of her mentally ill mother (a paranormal researcher) some months before. As she and her partner, Detective Justice, are in the middle of investigating the murders on the ship, Rita begins having strange visions about a woman who looks like her, and begins asking questions about her mother's past. When she tells Justice about having "a strange feeling" about the investigation, he is skeptical, which frustrates Rita. The visions are presumably influenced in part by her vampire heritage; this is hinted at a few times throughout the first two-thirds of the story. Rita is completely unaware of this heritage, and believes she is losing her mind, similar to what happened to her mother.
Meanwhile, Maximillian initiates a series of sinister methods to find out more about Rita and to further pull her into his thrall, including seducing and murdering her roommate Nikki, as well as disguising himself as her preacher and a lowlife crook. Max, in these disguises, misleads Rita into thinking Justice slept with Nikki, making her jealous and angry with him.
After saving Rita from being run down by a taxicab, Maximillian takes her to dinner. Rita is taken with Maximillian's suave charm, and begins to fall in love with him. While dancing with her, before he bites her.
Later the next day, Justice finds Rita in her apartment; Rita has been asleep all day with her apartment completely darkened. Justice informs Rita that Nikki has been found dead, and vows to help her understand her strange visions, as one of them had correctly foretold Nikki's murder. Rita tearfully forgives Justice, while berating herself for not listening to his side of the story, and is happy he is now beginning to understand her.
The two friends then embrace, and begin kissing passionately. Releasing these long-repressed emotions begins Rita's transformation into a vampire, and just as she is ready to bite the unsuspecting Justice in the neck, she sees her reflection disappearing in her bedroom mirror - a sure sign that she is transforming into one of the "undead". Horrified, she races to Max's apartment to confront him about the changes occurring in her.
However, Max explains himself, and by doing so, Rita, who already blames his biting her neck for "turning" her, deduces that he is also responsible for all the murders she and Justice are investigating. Rita further finds out that Maximillian was sent to her by her father (a vampire, making Rita a dhamphir), whom she has long been curious about; his death at the hands of vampire hunters was what drove Rita's mother insane.
Max tries to convince a hysterical Rita that she will be happier as a vampire instead of remaining in the human world, where he feels she will remain out of place and misunderstood by society. Justice plans to rescue Rita from Max, and seeks help and advice from Dr. Zeko, a vampire expert they visited earlier in the murder investigation. Zeko explains that years ago, he knew Rita's mother while she was doing her research on the vampires of the Caribbean islands, and that she surrendered to evil by falling in love with Rita's vampire father. To avoid becoming a vampire, Rita must refrain from drinking the blood of an innocent human victim; also, Maximillian must die before the next full moon. Zeko gives Justice an ancient dagger with instructions to either kill Maximillian or risk being killed by Rita.
By the time Justice reaches her, Rita is lying inside Max's coffin, almost completely changed into a vampire, and threatens to bite Justice. Justice and Maximillian engage in a battle, during which Justice loses Zeko's dagger on the floor. Maximillian encourages Rita to finish Justice off and complete the transformation. Rita rejects life as a vampire, and drives Zeko's dagger through Maximillian's heart, causing him to disintegrate; as her vampire self is heartbroken over the death of Max, she changes back into a normal human. Rita and Justice then embrace with a passionate kiss.
Meanwhile, Julius, now completely decayed, enters his master's limousine. He happens upon Maximillian's ring and puts it on, at which point he instantly transforms into a fully intact member of the undead. (It is implied that one of the benefits of his having been a ghoul is that he is now well-endowed). Overjoyed, he tells his uncle Silas, "There's a new vampire in Brooklyn, and his name is Julius Jones!"

Question: How did Julius become a fully intact member of the undead?
Answer: Put on Maximillian's ring