him into the academic firmament. Earlier, he had given him back his lucky T-shirt. In "The Art of Reckoning", Charlie is initially overjoyed to see his friend Larry return, but Charlie is dismayed with Larry's lack of enthusiasm in life, so Charlie doesn't object to him readjusting at a monastery. His concern is apparent, and he says he just wants his friend back. Since then, in "Trust Metric", Charlie is pleased to see his friend doing well, feeling that he needed a friend, and is glad to have focused on teaching while Don did not include him with FBI work; though, on previous occasions, he expressed the desire to be involved. Granger's escape from the prison bus causes him to become active in helping his brother once more, allowing him a chance to use set covering deployment. Dr. Finch tells him to publish, and so he has renewed interest in old research, having decided to publish one of his eleventh-grade papers he started at nine years old, "The Mathematics of Friendship," with an addendum. A publishing company has turned his work into a classic book for those not mathematically inclined, while opting for a title with more pizazz, "Friendship, As Easy as Pi." Charlie takes joy in the belief that this book will allow his thoughts to reach a much wider audience than before. By the episode "In Security," the published book appears with the title "The Attraction Equation" and a dapper photo on the back cover of him holding a sculpture of a stellated icosidodecahedron with bevelled edges. A decision theoretic approach to relationships is covered in the book. His proud father hands copies to friends and Larry sells signed copies on eBay. He apparently has some fans and gives into a televised interview. In "Checkmate", Charlie is training in weapons and tactics in LA's FBI school, where he is shown to have a high skill in marksmanship at the range, impressing many of his FBI training peers as well as his instructor, which he credits to following Wyatt Earp's preference for careful accuracy instead of rapid firing. He is given a certificate of marksmanship by the FBI. In the episode "Pay to Play", Charlie convinces Don to let him join the team when they go to arrest a suspect, mentioning that he passed the FBI course. In the season four finale "When Worlds Collide", Charlie helps an innocent