|“||Ian Doyle vanished from prison.||”|
— McCallister to Prentiss
Sean was tasked with becoming a member of a team organized by Interpol, codenamed JTF-12, which consisted of Prentiss, Clyde Easter, Tsia Mosely, and Jeremy Wolff. The team specialized with profiling terrorists for Interpol and helping it apprehend them. The team's most notable mission was sending Prentiss, under the alias of Lauren Reynolds, to infiltrate an organization led by terrorist Ian Doyle. After acquiring information concerning the organization's movements from the inside, Prentiss sent it back to Sean and the rest of the team and Interpol arrived at Doyle's residence and arrested him, but not before he realized Prentiss was a mole after watching her being taken away by two Interpol agents. The team was later disbanded for unknown reasons, and Sean moved on like all the rest, while Doyle was sent to a North Korean prison, though most of the team was informed the prison was located in Russia.
The Thirteenth Step
After finding out that Doyle escaped from prison, stabbing a motorist to death and stealing his vehicle in the process, Sean contacts the rest of his team, except for Prentiss, whom he is unable to get in touch with. He begins frequently pestering Prentiss with phone calls and text messages, unaware that she is busy on a case. When the unsubs are killed and the BAU close the case, Prentiss meets Sean at a restaurant back at Washington and apologizes for not returning his calls. Sean accepts the apology before telling Prentiss that Doyle escaped from prison and that her life is in danger. Afterwards, Sean goes into hiding in Brussels, Belgium with his wife and daughter (off-screen) and they are all eventually killed by Doyle's team. It is unknown as to how they were killed and if their deaths were disguised as casualties from a natural situation, just like the team did with all of their other victims, but JJ immediately managed to find out about their murders.