I had this strange thought come to mind while watching Sweeny Todd. If you would like to make a full length story out of this, go right ahead. Just put it in the disclaimer where you got the idea from. And yes the 'memory' that she sees is the movie.
I do not own or even claim to own the characters of Harry Potter. Though if I could I would so own Severus Snape and Bellatrix Lestrange and have them chained to a wall in my bedroom so I could play with them. (Yes I am sick and twisted)
Bellatrix was laughing as she chased the scared girl through the streets of downtown London. This is what she lived for, the fear, the pursuit. If only she could have shared this with her master. He did so love to see the filthy muggles put into place. The girl she was chasing was the older sister to a muggleborn witch that was currently at Hogwarts. However the sister had no magic in her. Her long brown hair flew out behind her as she ran. Bellatrix sent a blasting hex to the dumpsters on the side of the street right next to where the girl was. She screamed and started to run in a different direction. Bellatrix pursued her prey for over an hour before she saw the girl duck into a building with posters pasted over the walls. Bellatrix ran in after her but was stopped dead in her tracks at the amount of people in the room. The smell of popcorn, hotdogs and pretzels filled her nose and made her mouth water. She looked around and spotted her prey running down a carpeted hallway and then ducking in through a set of double doors. Bellatrix ran after her. Upon the doors closing behind her she realized just how dark it was. The main source of light was coming from one wall where pictures where moving and talking. Bella stood motionless in the shadows watching what appeared be some ones memory playing out on this wall.
The memory was just not any memory though. It was if the memory was that of the Almighty. The scenes would jump around, sometimes showing a man giving someone a shave, and then it would jump to a woman chopping up body parts and singing. Bellatrix found a seat and watched the rest of the memory and when the screen went black and the lights had come on she allowed herself to be steered through the crowd lost in thought, her prey forgotten.
When she arrived back at her masters headquarters she was still lost in thought. Voldemort noticed this and called out to her.
"Bella my sweet, what has gotten you so worked up?"
The voice of her beloved master snapped her out of her daze.
"My Lord, I was chasing that filthy muggle girl when she ran into a building. They were playing some memory that I have never seen before. I sat and watched the whole thing surrounded by countless other filth. The strange thing was that there was a woman in this memory that looked like me. She had partnered up with this man who would slice the throat of all who angered him. This man looked strangely like Severus, but this guy could actually sing." Both Voldemort and Bellatrix suppressed a shudder as they remember quite well how bad Severus can sing.
"Well after he killed the man, the woman that looked like me would then chop up the body parts and grind them for meat pies. She would then sell the pies to people in the town. I was just thinking how we could use the family members of the muggleborns that we kill and then send them the pies for the holidays."
Voldemort let out a deep laugh that sent sensuous chills down Bellatrix's spine.
"My lovely Bella, I just love how your foul mind works. Let's do it!"