Let's see. I'm going with the time frame being around the summer before Draco's 5th year. I'd say that sounds good before things blow up in his face and he's sent to Azkaban. Rating for cuss words, violence, implied slash.
Lucius was young and stupid when it started, not to mention displaying loyalty to his father, just like he was taught to do. He can still remember when his father brought him a muggle. He threw him onto the floor and said,"Look boy! Look at him! This is filth. They aren't like us, never will be, never will amount to what we are." He watched from a corner of the room as his father kicked the muggle man several times before muttering a few words under his breath while pointing his wand at the man. He writhed on the floor and moaned in pain. His father just laughed.
It wasn't until years later, with Tom Riddle finally having all he could take of his muggle relatives before he went crazy and boasted his plan to anyone who seemed to hate muggles or mudbloods. His father, aging quickly, decided that this was a great idea. Riddle didn't 'old' men in his ranks, instead, his father signed him over his self. Lucius was now forever in debt to Riddle.
Ok, so he acted like he enjoyed the acts. They were fun at first, it was wild, something to do when bored. Not to mention, this bought him respect with his father, since respect was lost when he found out his secret.
Lucius thought nothing of it. In fact, he thought it was beautiful, what he was, who he loved. He loved James. He wasn't always the horrible man you see in front of you now, he had a life, had hopes, had dreams, he just happened to be gay. How exactly he found out, Lucius is still not sure, he does know however, that a owl was intercepted by his father, the letter just happened to be from James. He stormed into his room late that night shouting at the top of his lungs,"What is this rubbish? What is this? Don't tell me you are hanging with James Potter of all people?" He said his name like a curseword, one that was utterly vile no one should ever dare speak it again.
"Nothing! Father I swear!" The first punch upside his jaw shocked him, but it was to be expected from him. He was a violent man, and you always would suffer at the hands of him.
"Nothing? Oh yes, this," he said waving the letter in front of his face before smacking him across the head a few times,"seems like nothing! " Lucius watched his father walk around the room reading the letter from his spot on the floor. One of which he was afraid to leave for fear of what might happen. "Oh, this is my favorite part." He paused and took a deep breath,"I love you so much Lucius, I fear we shall barely see eachother now since your father is being an asshole. Don't let that stop you, I love you and that's all that matters." He smirked. All Lucius rememebrs is waking up the next morning, not remembering what happened after that smirk.
Needless to say, Lucius and James were forced to keep their love a secret. They became enemies by day, people began to wonder what happened to the pair, pretty much everyone knew of their status, knew they were dating, so most figured it was a bad break up. Then, at night, when they were sure no one was around, they'd sneak off to be together, making love, often until the sun came up. It was perfect.
Before his father found out about his relationship with James, the arranged marriage to Narcissa Black had been put behind him, he would be free to marry whoever he wished, as long as he married a pure bloodline. However, as soon as it was out in the open, the arranged marriage was back on.
Don't think he doesn't love her however, he does, just not how he loved James. As expected of him, Narcissa gave birth, and more to the joy of his father, the child was a boy, someone to carry on the tradition of the Malfoy's. One, Lucius wasn't sure whether or not to continue.
Like a good son, Lucius continued his service with Riddle, who decided on the name Voldemort as his evil alias. Lucius worked with him so often and became so loyal, he soon worked his way into the inner circle, became Voldemort's right hand man. The only good thing he liked about the whole thing was the fear he could inflict on others. Others would cringe, some cower, others would just plain run into the other direction. It was about fear and money, something his father was sure to instill in him before his passing.
And now, as Lucius looks at his son, he can see the same thing repeating. Lucius is too afraid to break the chain. He wants too, wants to save his son from the life he will soon set upon if he doesn't do something soon. He can see it in his eyes, his son is in love with Harry Potter, except the two are enemies, day and night. He can remember when he recieved the letter from Draco saying how the daft fool had refused his hand in friendship,"Can you believe father, he refused to be friends with someone like me? Does he not know who I am? What I stand for?"
Lucius has never been that violent with his son. He threatens, but unlike his father, he cannot stand to hurt his son as much as he had been hurt. He's lost too much in his life time, especially the only thing he really ever cared for. He wants to stop the cycle, wants to stop the hurt. He looks in those grey eyes, sees everything he saw in him self, and yet, he cannot do it. It's all a part of his heritage, and heritage isn't something to lose.