Once in Paris, Nicki plays in the orchestra in the same theater that Lestat acts and wins his own modest share of acclaim; yet his spirit remains clouded. One night, amidst shouts and the sound of shattering glass, Lestat disappears. Although Nicki receives a message from Lestat a few days later, he cannot help but worry and feel the sting of betrayal. Longing to see his beloved, Nicki rejoices when Lestat reappears at the theater, but the joy is short-lived, for Nicki quickly discovers that his companion is no longer mortal, that he has been transformed into some monstrous creature. This fact is too much for Nicki to grasp and triggers his gradual descent into madness.

Things only get worse for Nicki, as he is soon abducted by Armand, who is engaged in battle with Lestat, and is kept hostage beneath les Innocents graveyard. The enraged Lestat appears, frantic over Nicki's safety, and succeeds in defeating Armand. Although stunned and weak, Nicki has not been so harmed by the "Children of Darkness" as to have his life jeopardized, and Gabrielle herself warns Lestat not to work the Dark Trick on his beloved violinist. In a moment of weakness and love, however, Lestat brings Nicki over to join the Savage Garden.

Made into a vampire, Nicki sinks into a state of shock, unable to speak or move. In an attempt to bring him "back to life," Lestat takes Nicki to the theater and stands him on the stage with his Stradivarius. Suddenly, as if a dam had broken, Nicki begins to play, his bow drawing out from the violin notes of such desperation and darkness that it gives Lestat physical pain to listen. This seems to have been cathartic and Nicki regains consciousness, but at the same time, he must face what he has become. This turns to overwhelming hate for Lestat, he whom he had loved so well before. Realizing that his presence can do nothing but to agitate Nicki, Lestat concedes to the violinist's demand that the theater be handed over to him, and leaving Armand to watch over Nicki, departs from Paris.

After Lestat's departure, the vampires succeed in establishing the reputation and fame of Theatre des vampires. The mad Nicki is the driving artistic force behind the theater's success, as he writes one play after the other, composing and playing the music as well. He had no qualms about revealing his true nature to mortals and is sloppy in his feeding habits, simply waiting to have someone realize what he is. It is left up to the other vampires of the theater to keep an eye on him and to watch over his conduct. Finally, Nicki's excesses enrage Armand to the point that the old vampire cuts off Nicki's hands. The hands were restored to him after several days, but the pain and excrutiating suffering must have gotten through his madness to the last core of sanity left in his soul. After a few days of silence, he requests Armand to hold a huge Sabbat for him. Armand acquiesces; the entire theater coven join in the ceremony and stand as witnesses, as Nicolas enters the fire and ends his miserable existence.