|Hannah is first seen during an incident Captain Gregson has with her partner, Officer Stotz. Captain Gregson punched Stotz in front of many officers for molesting his daughter. Hannah demands her father shake Stotz's hand at roll call and tells him to not protect her anymore as she's capable of taking care of herself and has career ambitions. ("Rip Off") She's next seen asking Watson for help with a rash of pharmacy robberies in her neighborhood. Watson solves the case and believes Hannah is dedicated but green. Holmes believes she is a middling detective at best and doesn't have a future as one. Instead of following Watson's advice to hand the case over to her superior and take down a drug ring, Hanna apprehends the robbers in order to get credit. Eventually, Hannah feels guilt and tells her father who requests that Watson not help her with any more cases. ("A Stitch in Time")|
|Hannah, now a sergeant, visits her father at the 11th Precinct with concern on her face. Gregson later tells Watson that Hannah is an alcoholic and is undergoing treatment. Later at her home, her roommate Maddie tells her that a man just hit her car and wants to see her outside. The man is Michael Rowan who exchanges information with Hannah seemingly in order to pay for the damage he's caused. Later that evening, Michael is seen sitting in his car as Hannah comes home and finds Maddie murdered. ("Give Me the Finger")
|The police arrive and her father Tommy comforts Hannah and questions her about Maddie's murder. Hannah can't think of any suspects and says that Maddie was a very nice person. She does say that Maddie's body looked posed. Detective Bell reports that there are no clues at the scene. Tommy insists that Hannah stay with him and Paige that evening. After Sherlock suspects Rowan is the killer, Hannah comes to the 11th Precinct. She identifies Rowan as the man who hit her car and was going on a date with him when Maddie was killed. Rowan texted Hannah that he couldn't meet her. Hannah feels she's to blame for Maddie's murder and offers to wear a wire and ask Rowan on another date but Tommy and Watson indicate they already have someone close to Rowan. ("Sober Companions")
|Unknown to Holmes and Watson, Hannah investigates Michael on her own. After he assaults Watson and is wounded, Hannah deduces that Michael will go to the home of a friend from support meetings, Denny Mulgrew, who was a field medic, to be stitched up. Hannah waits until Mulgrew leaves and enters the house, planning to shoot Michael. She decides instead to beat him to death with a baton, not knowing that he was leaving a voicemail that records the murder, including his last word "Joan", which Hannah doesn't hear. Hannah then uses an accomplice and a garbage truck to dump Michael's body in a dump. After Watson is implicated in the murder, Holmes discovers that Captain Gregson erased video evidence from the garbage truck depot to aid Hannah. Holmes meets Hannah, has her produce the murder weapon and then he confesses to the crime. ("Whatever Remains, However Improbable")
- Captain Gregson mentions Hannah is still with the NYPD after the Michael Rowan incident. ("From Russia with Drugs")
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