Nicholas Ruskin

Det. Nick Ruskin is the main antagonist of the novel Kiss the Girls and the 1997 film of the same name. He was a serial killer who kidnapped beautiful women under the name "Casanova".

He was portrayed by Cary Elwes in the film, who also played Edgar and Lawrence Gordon.

Backstory
Not much is known about his past or how he he came to be what he was. What is known is that when he was a teenage boy, he snuck into Coty Pierce's, a girl he went to highschool with, home where he spent his time in the attic, watching her and her family through the vents. One night, he finally decided to sneak out of the vents to commit "the perfect crime", and raped and killed Coty, her sister, and her mother.

Some time later, he met Will Rudolph in college. It's not explained how, but he found out that he had killed a young couple and convinced him he could trust him. The two then formed a bond and began on their own murder sprees together.

He eventually became a detective for the Los Angeles Police Department, which not only deceived the cops as he gained their trust, but also gave him the chance to change the dates of the kidnappings so he would have alibis.

It's also stated in the novel that he was in fact married, but had somehow managed to go on his killing sprees without her knowing.

Methods
Unlike his accomplice, Will (aka The Gentleman Caller), who was very brutal and cold blooded in his nature, Nick was more calculating and reserved, selecting women based on both physical beauty and their personality. In his mind, they loved him as well. After he kidnapped them and took them to his lair, he would rape them and make sure they didn't brake any of his rules, which meant trying to escape or talking to each other. He apparently suffers from Dissociative Identity Disorder, as he wears different masks depending his personality. If any of the girls broke his rules, he would take them to the woods, tie them to a tree, cut their hair off as his own way of punishment, and leave them to die. What makes him unique among psychopaths is that he "empathizes" with his victims.

Defeat
Nick would eventually meet his demise when he kidnapped Alex Cross' daughter, Naomi, as well as Kate McTiernan. After Kate escaped, she encouraged Alex to track him down even further after she informed him that she spoke with Naomi. Time passed on as they discovered more clues leading to their discovery of The Gentleman Caller. As they got closer, both Nick and Will  broke into Kate's house and put beat Kate into a coma for a while. Later in the novel, Alex and his partner, Sampson, discover where they are both keeping the women and make it to their hideout. Nick and Will are both watching them and take Sampson out while Cross finds Naomi. Cross hears Sampson scream and runs to find both Nick and Will, wearing masks, on top of his partner with a knife stuck in his back, but still alive. Cross takes his gun out and fires at them, hitting one on the shoulder. The two take off running and make it to a nearby bar, steal a truck and drive off. Cross takes a car and goes after them. In traffic, the two run out of the car, running opposite directions and firing their guns. Cross follows one, they exchange gunfire, and he hits him in the chest. Cross runs to the man and takes off his mask, revealing him to be Rudolph. He dies telling Cross that he will never catch Casanova. This results in him going into a breakdown after he losing his "twin". Once Kate is out of her coma, Alex visits her,  goes  jogging and finds a dead FBI agent. He runs back to the house where Nick hits him with a stun gun. With Cross down, he heads for Kate, but Kate fights him and takes him down. He takes out his gun to shoot her, but Cross gets up in time to shoot and kill him in self-defense.

In the Film
In the 1997 film of the same name, not much is changed about Nick Ruskin's character or his backstory. Although how he met Will Rudolph is omitted, as well as them putting Kate in a coma. His fate is changed as well. He tears out the glass tubes in Kate's kitchen after she's fought him off  and attempts to blow them both up with his lighter. When Cross arrives to try to talk him down, he gives a speech about how he feels his "animal self" comes alive any time he looks at a beautiful woman and that he merely wants to break them down through rape and torture, and how Cross, deep down, is no better than him. He also taunts him about how he raped his niece the whole time he had her in captivity for more than a week. He attempts to turn on the lighter, but before he can do so, Cross manages to shoot  and kill him through a milk carton so the muzzle blast from his pistol does not ignite the gas.