Bob Ruzek is the first to arrive on the scene of a double murder. Intelligence arrives to take over the investigation and tensions arise as Bob needs to hand over the case to his son and Voight. Lindsay's new gig has her planning a trip to Bolivia for an undercover investigation that could be for an extended amount of time. Burgess and Roman realize they need to put past events behind them so it doesn't jeopardize them going forward.

While undercover, Ruzek discovers his father is working for a suspected drug dealer and is forced to ask the question: is his dad involved?

Ruzek's father, Bob, goes missing and the team races to find him before it's too late.

An unexpected visitor causes disruption for Ruzek and Burgess amidst an emotional investigation involving an unidentified young girl.

Ruzek grapples with his father's worsening condition while Intelligence searches for an elusive serial killer.

Ruzek witnesses a tragic accident on an icy bridge, leading Intelligence into a dark, sinister case involving sex trafficking.

Forced to cease operations while under investigation by Internal Affairs, Intelligence goes off-book to bring down Reid once and for all. Ruzek and Burgess consider delaying their nuptials amid the uncertainty.