Plot summary
Charlie focuses his attention on tracking a previously undetected serial killer to help deal with his guilt over Don's almost-fatal stabbing. He receives help from a geeky amateur sleuth and a retired accountant, who each research serial murders as a hobby. The investigation reveals that the killer may be responsible for over two dozen unsolved deaths. Josh Gad reappears in his previous role as a conspiracy theorist. John Rubinstein, Matthew Yang King and Brian Howe also guest star.
Credits
Adapted from Wikipedia contributors, Numbers season 5. HTML formatting and reference markers removed.