The world has long lost its voice. No more human laughter, no more footsteps on the streets. All that remains is the crunching of bones and the faint screams of the dead and the directionless, the zombies.

You've survived months on your own, moving from place to place. Every night you sleep with a knife in your hand and every morning you wake up with the slim hope that someone else might still be alive.

Until one night in a desolate city, when a pack of zombies almost swarms you, someone pulls you by the hand into an old building. The man is tall, dusty, with a fresh-looking wound on his neck. His eyes are sharp, but his voice is calm.

"Don't move. They can smell fear."

His name is Sergei Antonov, he is a scientist. He used to work in the lab that created the Z-01 virus, the cause of all this destruction. But now, he lives in guilt, trying to right the wrongs he helped create.

When you realize he's one of "them", you almost run away. But Sergei shows you a small vial of blue liquid.

"I'm infected... But this serum keeps it at bay, but not forever. I have to find the perfect version or I'll change completely."

That night marks the beginning of your journey. You and Sergei traveled through dead cities, searching for clues to create a permanent cure. Each night you took turns sleeping, and each morning you woke him up with a glass of water, making sure he was still conscious.

Along the way, you see a different side of Sergei. He was no longer the cold scientist who spoke in a flat tone, but a gentle man, who looked at you every time you chuckled over something trivial. Sometimes he would stare at you for a long time, as if afraid that one day he wouldn't be able to remember your face.

"If I change... please don't cry for me," he said one night under the rain. "I'd rather die by your side than live as a monster."

But you looked at him sternly.

"You're not a monster. You're a human trying to save the world and I won't let you give up."

Your journey takes you to the central laboratory by the sea, where the Z-01 virus was first created. There, you meet a group of survivor soldiers still fighting to finish off the zombies. They recognize Sergei as a "world traitor", but you stand in front of him to protect him.

"If you blame him, you'll have no hope. He's the only one who can heal this world!"

Finally, after many weeks, you managed to create the Z-01 Reversal vaccine. The army helped spread it through the air, and one by one, zombies began to fall, not from death, but from turning back into humans.

But before it was over, the serum in Sergei's body stopped working. The virus began to reactivate. His body trembles, his breathing quickens, and his eyes turn red.

You hugged him tightly in the middle of the laboratory that was shaking with the sound of explosions.

"Hang in there, Sergei... Please...."

"I... I don't want to hurt you..." his voice is hoarse, almost inaudible.

"You won't," you reply softly, "because I trust you."

You inject the last dose of vaccine into his veins. A few seconds feels like an eternity and for a moment, you think you've lost him.

But then, he opens his eyes. His blue eyes aren't red anymore. His hand grips yours tightly.

"I'm... still here," he whispers.