Ralph Rodriguez

Danny believes a serial killer is on the loose when two separate murder victims are identified as members of a group charged with gang rape. Meanwhile Erin's ex-husband, attorney Jack Boyle, resurfaces in her life as they face off in court. Peter Hermann guest stars.

Members of Firehouse 51 are less than thrilled when Captain Patterson (guest star Brian White) steps in as replacement for Chief Boden (Eamonn Walker) while he deals with clearing his good name. When Severide (Taylor Kinney) learns of the potential whereabouts of Serena (guest star Ilfenesh Hadera), Chicago P.D's Officer Atwater (LaRoyce Hawkins) and Officer Ruzek (Patrick John Flueger) head to Lake Carlyle to try and uncover additional clues on Boden's case. Meanwhile, Herrmann (David Eigenberg) and Otis (Yuri Sardarov) give Freddie (guest star Ralph Rodriguez) a job that keeps him close by and Jimmy (Steven R. McQueen) and Chili (Dora Madison) elicit more attention then either bargained for, causing some friction between them.

Herrmann (David Eigenberg) goes to court to testify against Freddie (guest star Ralph Rodriguez), but when the perpetrator's father (guest star Ski Carr) reaches out to beg forgiveness for his son's malicious attack, a tormented Herrmann is left to figure out what to do. Following the aftermath of the recent tornado, Lt. Casey (Jesse Spencer) learns the makeshift shelter housing victims is on the brink of shutting down. At the request of Alderman Colin Becks (guest star Armand Schultz), Casey attends a fundraiser and is thrown into the spotlight, only to quickly discover that his good intentions might not have the impact he was hoping for. Dawson (Monica Raymund) and Brett (Kara Killmer) feel the repercussions after telling Boden (Eamonn Walker) about Chili's (Dora Madison) recent erratic behavior. Meanwhile, Severide (Taylor Kinney) helps Agent Alex Ward (guest star Liza Bennett) solve a homemade explosives case, and Otis (Yuri Sardarov) receives a welcome surprise.

Chief Boden (Eamonn Walker) meets his new neighbor (guest star Ilfenesh Hadera), who asks him for a favor that leads to serious consequences. Severide (Taylor Kinney) takes offense to being treated like a candidate by Captain Patterson (guest star Brian White) by undermining him during a call, and the situation reaches a boiling point. Cruz (Joe Minoso) receives a surprise visit from his past when Freddie (guest star Ralph Rodriguez), a gangbanger who knows Cruz's brother Leon, comes to visit and ask for a favor. Elsewhere, the team is called to a harrowing scene of an 18-wheeler and receive a thanks in the form of tickets to see the band Rush, much to Mouch (Christian Stolte) and Herrmann's (David Eigenberg) delight.

A tornado threatens the city and Herrmann (David Eigenberg) discovers the path may hit close to home. Chili (Dora Madison) and Brett (Kara Killmer) lock heads when Chili makes a critical mistake that leaves a victim breathless, prompting Brett to report to Chief Boden (Eamonn Walker) regarding Chili's erratic behavior. Meanwhile, Otis (Yuri Sardarov) pleads for Dawson (Monica Raymund) to help him solve his women troubles, and Severide (Taylor Kinney) is asked to lend assistance to agent Alex Ward (guest star Liza Bennett) from the Department of Homeland Security regarding a suspicious home.