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FBI Season 8 Episode 18 Preview: Maggie Pairs with Peter Olsen in ‘Behavior’

April 16, 2026

Zach Grenier (The Good Fight) reprises his guest-starring role as Peter Olsen on CBS’s FBI season eight, episode 18. Directed by Peter Stebbings, episode 18 – “Behavior” – will air on Monday, April 20, 2026 at 9pm ET/PT.

“Behavior” Plot: When a single mother and her son are abducted while visiting a state park, Maggie brings in Peter Olsen to help profile their suspect. But as the team works, they make a harrowing discovery about an old case.

Missy Peregrym stars as Special Agent Maggie Bell, Zeeko Zaki plays Special Agent Omar Adom “OA” Zidan, Jeremy Sisto returns as Assistant Special Agent in Charge Jubal Valentine, Alana De La Garza is Special Agent in Charge Isobel Castille, John Boyd stars as Special Agent Stuart Scola, and Juliana Aidén Martinez plays Eva Ramos.

FBI Season 8 Episode 18 — Missy Peregrym as Special Agent Maggie Bell and Zach Grenier as Peter Olsen in ‘FBI’ season 8 episode 18 (Photo: Bennett Raglin © 2026 CBS Broadcasting, Inc)

FBI Season 8 Description, Courtesy of CBS:

FBI is a fast-paced drama about the inner workings of the New York office of the Federal Bureau of Investigation. This elite unit brings to bear all their talents, intellect, and technical expertise on major cases in order to keep New York and the country safe. Born into a multigenerational law enforcement family, Special Agent Maggie Bell commits deeply to the people she works with as well as those she protects.

Her partner is Special Agent Omar Adom “OA” Zidan, a West Point graduate via Bushwick who spent two years undercover for the DEA before being cherry-picked by the FBI. Overseeing them is Special Agent in Charge Isobel Castille, who operates under intense pressure and has undeniable command authority.

The team also includes Assistant Special Agent in Charge Jubal Valentine, the nerve center of the office, whose ability to easily relate to and engage with both superiors and subordinates makes him a master motivator, as well as Special Agent Stuart Scola, an Ivy League-educated Wall Streeter-turned-FBI agent. These first-class agents tenaciously investigate cases of tremendous magnitude, including terrorism, organized crime, and counterintelligence.