...or what happened before he lost his body.
It was a normal day, Voldemort (still looking like Tom Riddle) was sitting at his throne, in his hand he clutched the diary he made when he was in his youth. Bellatrix stood before him, currently indulging in staring unabashedly at her crush, or in her words, True LOVE! The Dark Lord knew she would protect the diary, she was after all one of his best duelists and most trusted. She would follow his orders to bring him back should anything happen to him. A full Death Eater meeting was due to start in a few minutes, but he wanted to get this done first.
"Bellatrix," the Dark Lord began, "I have called you here in order to give you a most important task. I..."
"Yes, my lord. I'd do anything for you my lord!" she interrupted, batting her eyelashes.
"Yes, well," he was a little unnerved at the unabashed flirting, maybe this wasn't the best plan, ah well, "this here is an enchanted diary I made in my youth, I need you to hold on to it and write in it only if something should happen to me. If the unthinkable should happen, the diary will tell you what to do." He finished, handing over the diary. About this time, Lucius Malfoy came through the throne room door.
""Bellatrix squealed, clutching the diary to her chest. Okay, this really was a bad idea, Voldemort thought to himself.
"Accio diary!" he yelled, throwing the diary to Lucius, "Take this and run, protect it with your life, I suggest hiding."
Lucius caught the diary and took off, Bellatrix had started for him the minute the diary left her lord's hand.
"Crucio!" she yelled, it came with almost no thought, being her specialty and all. However, the door slammed shut before it could reach Lucius.
He ran down the hallway, dodging cruicos as Bellatrix ran after him. He knew if he could only make it to the apparition point he would be okay. The other Death Eaters who had gathered for the meeting stood to the side, hoping to avoid the flying curses and unwilling to get involved because who knew which one was actually working for their lord.
...and this is why had Voldy retained his sanity Bellatrix would've never been his consort. Alas, he didn't and so she was...