3 ideas
Captain Mat Joubert of Cape Town's Murder and Robbery unit has spent two years overweight, chain-smoking and barely functioning since his wife Lara, also a police officer, was killed on duty. A new commanding officer brought in to modernise the unit orders him to lose weight and see a psychologist or face sidelining. He must meet those demands while hunting a killer who shoots apparently unconnected men with an antique Mauser pistol.
When an institution is remade from above after regime change, the new leadership often imposes measurable standards such as fitness, psychological evaluation and procedural modernisation, and uses them to sort the old guard. Veterans experience these tests as tools for pushing them out rather than as neutral improvement. The measures can be both politically motivated and substantively right at the same time, which makes resistance to them hard to justify.
Killings that look random usually have a hidden selection rule, and the killer's distinctive signature, such as an unusual weapon, marks the killings as a series before the rule is known. The investigation therefore shifts from studying each murder to asking what the victims have in common, which is often found in their history rather than their present lives.