Not much is known about Nicholas' background, except that he is either very wealthy or comes from a wealthy family, because he can afford a trip to Delos Park.
Nicholas was a guest in The Raj, where he met a beautiful woman named Grace. After flirting, the two engaged in sexual activities. Grace, a guest herself, did not want to have sex with a host, so, after an arguement with Nicholas, shot him. The bullet only stung him and the two started having sex.
Later the two went bengal-hunting in the jungle. It appears the two have started to have an closer relationship, but it was cut short, as the two guests discovered two other guests, killed. They were attacked by Ganju, a host, who said "these violent delights have violent ends", before shooting Nicholas, killing him.
Nicholas was Emily's lover in the Raj, though it's not clearly known for how long. It seemed that Nicholas might have had even feelings to her, since he embraced her during their hun. It's not known if she felt anything towards him. His death shocked her, though she hasn't shown much emotion about him since.