Paul Friedman appeared in the episode Red In Tooth And Claw. He was the killer of Linda Parfey.
Linda came to the lab with a new species of moth that she found in the forest. Linda baited few with brown sugar and caught one of them and brought it to Paul because she was unable to identify them. Paul realized that it was a new species. Paul’s recent paper was rejected and so he needed to find something new to survive. He knew that this was his moment. So he killed Linda and put her in the tank and filled it with worms.
He then used her moths to save his job, get accolades, and grants.