It had to come down to this eventually.

The "rat man," as Chell found herself calling him, has been a thorn in Hypatia's side for long enough. He's been spotted before and always managed to evade capture, but she intends for this time to be different. Hypatia's made the consequences should she fail again clear.

As she approaches the place where he was seen, Chell wonders why it feels so wrong.