Caitlin Snow: Neural oscilations are normal. You three are perfectly healthy. Oh, and we think we've figured out how you two ended up in Nora's brain.
Cisco Ramon: That is a satellite shard full of dark matter in Grace's head.
Sherloque Wells: Mon dieu.
Caitlin Snow: Sometimes surgeons leave a piece of shrapnel in a patient's brain if it's too dangerous to remove, and we think that the dark matter was seeping out to create a barrier around her brain. We can't go back in as long as it's there. It's too dangerous.