Brooke first appeared with her mother, Ruth, as they encountered Thomas Magnum regarding Ellis' murder. Hani Iona, a longtime friend of Theodore "TC" Calvin, was suspected and charged with Ellis' murder, as Hani was one of Ellis' patients. Despite more evidence and a possible motive (owing Ellis money) making things difficult for Hani, Magnum received information from the autopsy that revealed that Ellis' killer was female.
A brunette hair found on the body led Magnum to a woman named Daisy Chase, who was believed to be Ellis' mistress. As it turned out, Daisy was Ellis' business partner in his side profession: selling PEDs for profit. After she was saved from a fighter named Wade Steuben, Daisy revealed her partnership with Ellis, while wondering why many people think they were having an affair. Her last comment led Magnum to the truth: Brooke was Ellis' killer.
Brooke had noticed that Ellis was around Daisy quite a bit, and that led her to believe that they were having an affair. She later confronted her husband at a parking garage, pointing a gun at Ellis while voicing her anger over his betrayal. Brooke turned heel and shot Ellis to death in a fit of rage, and she left the gun behind as she fled the scene, with Hani arriving after the murder occurred. Because of this, Hani ended up accused of killing Ellis, and in the episode's climax, the evil Brooke received a phone call from Magnum asking her to fly to Oahu for information on the case, using the departure to take Brooke's laundry to find clothes covered in gunshot residue.
Later on, Brooke was interrogated by Detective Gordon Katsumoto, but Magnum figured that the only way to truly expose Brooke as a villainess was to get a confession out of her. After TC was sent to distract Katsumoto, Magnum entered and revealed the truth: Brooke killed her husband under the belief that he was having an affair with Daisy, but they were partners in a side job, with Ellis selling the PEDs to keep up with his wife financially and keep her in the wealth she grew up in, doing so out of love for Brooke. At that moment, Brooke tearfully confessed, claiming that she killed Ellis by accident and that murdering her husband wasn't her intention. Brooke's confession came just as Katsumoto re-entered the interrogation room, leading to the villainess being arrested (off-screen).