In "Face Off," the team was shocked when they realized the serial killer had Isobel Castille's home address. Since they were actively trying to stop him, it made sense that Isobel would be the murderer's next target. He had every reason to go after her.

Audiences were in a panic when the suspect broke into Isobel's house and the two engaged in a struggle. However, Isobel was not only able to fight him off, but she broke the case wide open.

Isobel understandably got a good look at the killer's face, allowing the team to realize that they had misidentified him because he was wearing a mask (hence the episode title). She didn't let him get the upper hand on her and he ultimately ran off.

And she proved once again why she's the boss. Even after coming that close to potential death, she charged forward with the investigation. Isobel trusting her gut allowed the team to capture their suspect and save his young daughter.