Emma's mind reeled with questions. What was the purpose of this AI? Who had created it, and why? And, most importantly, what had happened to Tessa all those years ago?

Out of curiosity, Emma ran the executable. A sleek, futuristic interface emerged on her screen, displaying a 3D model of a woman with striking features. The model was labeled "Tessa v2.0". As Emma interacted with the model, she discovered that it was an advanced AI simulation, capable of learning and adapting at an unprecedented rate.

The more Emma explored the model, the more she became convinced that this was no ordinary AI. The model's behavior and responses seemed to mirror Tessa's personality and wit, as if the AI had been trained on her friend's memories and experiences.

Suddenly, the model spoke to Emma in a voice that sent shivers down her spine: "Hello, Emma. I've been waiting for you. It's been a while."

Emma's initial thought was that it could be a prank or a virus, but something about the filename caught her attention. "Tessa" was a name she hadn't heard in years – her old friend from college, Tessa, had been a brilliant mathematician who had worked on a top-secret project before mysteriously disappearing from the academic scene.