Ralph Fiennes: How “evil” is Lord Voldemort? He’s a demonic spirit. He’s a satanic force. Young Voldemort was an orphan and denied any kind of parental affection or love, so he’s been an isolated figure from a very young age.

But I always think there has to be the possibility of good in someone, too. It might have been eroded, repressed, suppressed, or somehow distorted within him after he was really damaged.

At first, I wasn’t sure I wanted to play him, and I wasn’t familiar with the books. I still haven’t read Harry Potter and the Sorcerer’s Stone. After I got the role, I pored over all the references in the books and found the passages where J. K. Rowling described him. Sometimes you can create a character off a real-life person, but often you create something out of yourself.

As it turned out, I very much had a part in the way he looked. I found little physicalities in the role, and something always happened when I put those long, flowing robes on. That’s when I felt Voldemort.

I would come to the set in the morning, usually at around 6 a.m., and the whole process would take about two hours. I’d have my scalp completely shaved; they would put sickly reptilian skin on my hands and cover my eyebrows with prosthetic pieces.

In the book, Rowling described his glowing red eyes. I’m really glad they didn’t do that in the films. I would have these long fingernails glued on, and I couldn’t clench my fists or I’d break them. The designer made a wand with a hook like a bird’s claw at the end, and sometimes I would let it hang from one of my fingers. I don’t have the wand, but I did keep the very convincing dentures they made for me. They’re in a jar in my study.

As for his loneliness, I do understand it. I don’t think he’s ever had a love life. He doesn’t know what love is; it’s a language he doesn’t understand. He’s all about acquiring power and controlling and manipulating a lot of people. It can be thrilling and quite freeing to play, because all the rules disappear. In Harry Potter and the Goblet of Fire, director Mike Newell encouraged a switchblade explosion of venom and rage. When somebody is contained and has the ability to explode, that makes people nervous.

When I was young, there was this character in Chitty Chitty Bang Bang called the Child Catcher. I remember being terrified by this figure. I think children should be really scared of Lord Voldemort.

Sometimes kids would come to the set, and I could see them looking at me anxiously. I once walked past the young child of a script supervisor, and he burst into tears. I felt very good about myself.

I don’t miss the character. I have a sense of completion. Everyone was wanting it to come to its grand finale.

Some actors enjoy signaling the evil in characters called “bad guys,” but you want to be a human being first of all. Everyone has the potential to be corrupted. Everyone.