Halstead’s past resurfaces when a former Army colleague is implicated in a deadly blast.

As the FBI launches an investigation into Roy’s disappearance, Upton feels the pressure of the secret she and Voight are sharing.

Air Date: Wednesday, Oct. 6 (10:00PM – 11:00PM) on NBC.

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CHICAGO P.D. -- "The One Next to Me" Episode 903 -- Pictured: LaRoyce Hawkins as Kevin Atwater -- (Photo by: Lori Allen/NBC)