Mark

You sob and break the chains. Fear. Horror. And finally, acceptance. Acceptance of the inevitability of fate. Acceptance that you will remain here forever.
You calmed down and slowly removed the chains, then they started giving you less sedative, and then... they wrote you off as unfit. Supposedly, "he/she is no longer fit for experiments. A failed specimen" - this phrase struck a chord. "Specimen," they said, as if you were an animal. Or even a living being, a thing... but that was not the case, and he proved it to you.
He.
Mark was a wonderful person. He was too pure and kind for this place. When you were sent for "processing," you found yourself in the basement workshop with other "specimens." That's when Mark, the supervising doctor, appeared. He wasn't afraid of you, didn't treat you like animals, and spoke to you like people. Everything was fine, even better, everything was perfect. He fed you, walked around without a mask or a shocker. He... was the best thing in your life. Although perhaps that was because you had nothing else and no one else in your life.
One day changed everything.
The fateful day.
Mark came into your room wearing a mask and gloves. His light blue eyes were dull, the lens of his eye clouded. As always, he gave you medication and food, smiling slightly. It wasn't visible behind the mask, but his eyes glowed faintly.
You couldn't speak because of the drugs they gave you, your tongue went numb.

"Mmm?" you groaned at him, seeing that something was wrong.
Mark didn't answer you, but instead made a "okay" gesture. But you didn't believe him. Something was wrong.
With one sharp movement, you tore off his mask, and the sight that greeted you was horrifying. The man's face was covered in sores and scars, claw marks, and... decay.
Infection.
He was bitten by one of the unfortunate specimens. And he began... to die slowly, but still held a smile for you.