Living with his father in a mansion, Daniel became terminally-ill. To save his son's life, Curien researched breaking the barriers between life and death. Businessman Caleb Goldman funded the project, but Curien eventually went mad and released his creations upon staff members. He died at the hands of his "masterpiece", the Magician. Daniel, however, was cured.
After his death, Curien's body underwent a transformative process, becoming a powerful entity called the Wheel of Fate; for nineteen years, Daniel oversaw this development within the EFI Research Facility.
By 2019, civilization had collapsed following a pair of outbreaks caused by Goldman in 2000 and 2003. To find the source of humanity's downfall, AMS agent Thomas Rogan lead a group of military commandos into the facility. Eventually the only survivors, Rogan and captain Dan Taylor discovered where the Wheel of Fate was held, but Death, one of Curien's creations, killed Dan and injured Rogan. Daniel appeared and rescued Rogan.
When Rogan's daughter Lisa and former partner "G" investigate two weeks later, they eventually meet Daniel while reuniting with Rogan. Willing to bear the burden of his father's crimes, Daniel teams with Lisa against the Wheel of Fate. Although the being begs for forgiveness, Daniel angrily refuses to recognize it as his father and mercilessly kills him.
Feeling that he has finally moved on in his life, Daniel bids his father farewell, but vows to return to the EFI Research Facility should humanity be threatened again.
In flashbacks, during which Daniel is bedridden and in a comatose state, he wears light-green pajamas.
As an adult, Daniel appears with blue eyes and short brown hair, which has half fringes on the left. He wears glasses like Curien, and is seen in a formal brown suit jacket, a gray long sleeve undershirt, and black pants and shoes.
In the "bad" ending of The House of the Dead III, he becomes a pale-skinned and monstrous-looking zombie.
Each flashback shown at the beginning of each chapter shows Daniel bedridden while Dr. Curien talks to him, usually about the progress he makes in his mission to save Daniel from whatever disease he may have. The flashbacks also give some insight to Dr. Curien's constantly slipping grasp on sanity as he struggles to help Daniel.
Daniel is seen bedridden with what appears to be a terminal disease. Curien is sitting at his bedside saying that no matter what the doctors say, he will do everything to save his life, even if it means stepping into "forbidden territory".
Curien is now leaning over Daniel, this time with hope in his voice as he holds a mysterious glowing canister given to him by Goldman (or perhaps directly by the late Clement Darling) which he refers to as "the key that will break the barrier between life and death" (which is either a compound of his own creation or that of Clement's). He assures Daniel that he no longer has to be afraid of anything anymore, not even death.
Curien is sitting at Daniel's bedside again, contemplating what he's been doing lately. He asked a quiet Daniel if he's gone over the limits of morality, since most of his researchers have left him.
Curien rushes at Daniel's bedside, this time ridden by madness, possibly due to the nature of his experiments. In a maniacal manner, Curien claims that "he found it": genes that will supposedly change the future, referring to them as "The Magician" and "The Wheel of Fate", ending with diabolical laughter.
- Daniel's ultimate fate at the end of the game depends on the player's progress throughout the game:
- If one or both players get any rank below an A or S, the normal and best endings will be shown depicting Daniel showing no adverse effects of his life with his father and follows Lisa in leaving the area (with or without the jeep Lisa and G drove in with, depending on the ending).
- Ironically, if one or both players gets an A or S rank, Daniel would stop moving and show little will to go on, prompting Lisa to witness him becoming a zombie and attack her, possibly due to the adverse effects of Curien's "cure" to his illness.
- It is unknown which of these is canon and whether or not Daniel is infected or, if so, whether or not the adverse effects are active (making him a zombie) or dormant (making him potentially become a zombie later).
- Daniel's age in childhood or being grown up is confirmed to be "CLASSIFIED". Because the reason he's grown up by effects on the blue vial where he was already cured by his father before 1998 Curien mansion Incident being happens. Or he grown up normally after he is on the destroyed facility filled with zombies.
- Based on the promotional trailer, at the time which a Mysterious Man appeared with a mysteriously satisfied smile, his evil appearance, a cutscene from the game, in which G claiming that "Someone IS trying to continue his (Roy Curien) legacy" and his introduction, it is possible that Daniel Curien was initially set to be the mastermind of the game. However, the creators might have thought that that idea was getting old. So, they created a much more dramatic story, in which Daniel is a good man, spending his whole life fixing his father crime.
- Daniel is voiced by Kevin Miller, who also provided the voice of Sly Cooper, the main character from the video game series of the same name.
- He has a slight similarities to Evil Within's tritagonist Joseph Oda, both of them are helping their colleagues in terms of fighting the enemies and transform to monster (in Joseph's case, he turned to his haunted form only when in gameplay while Daniel does zombie form just to kill Lisa in Bad Ending).