Once he sees that determination echoed (at least a little) on Fuu's face, he removes his hand and stands up from the couch. While they could continue to sit there and try and figure out what the nails and that bitty symbol mean, it means that much more time that the murderer has to try and hurt other people.

Even though it's dangerous to go, it's dangerous for the others if they stay. And, in general, Jamie prefers to be doing something rather than sitting about.

"Right. So are ye ready to go, then?"