Two tourists are shot by a man dressed as a cop. Danny has arranged an intervention for McGarrett, to get him to take his health more seriously. Danny lined up a stress-management consultant to shadow McGarrett for a day. The tourists recorded their murder, but Duke says the cop who shot them supposedly died years ago. So someone else  is using his identity. Danny and McGarrett go to the house of the cop's widow, only to find her dead. The son, Oliver, has gone off his psych meds, with his mother's death the stressor. Dressed in his father's old uniform, Oliver breaks in a home, where he used to live, and beats up the homeowner. Alicia Brown diagnoses Oliver as having dissociative identity disorder. Chloe tells Danny he's adding to McGarrett's stress and urges him to be more agreeable. Oliver's psychiatrist tells Alicia that Oliver has seven distinct personalities. Oliver has killed another man. Oliver shows up to HPD, and Duke locks him in an office, but Oliver escapes through the roof tiles. The team searches the building for him, but he gets out and steals a squad car. They corner Oliver, but he threatens to kill himself. So they barricade him in his home. Alicia wants to go in to speak to Oliver, hoping to break through to him. She's garbed in his mother's dress and she makes him lunch the way he liked it, drawing out the 5-year-old Ollie personality and getting the gun away from him. Chloe gives McGarrett a long list of recommendations for manage his stress, which he poo-poos. Danny admits he's scared for McGarrett, and McGarrett admits he's scared as well. They agree to just be themselves around each other.