Venn Diagram Manhunt
Highlight areas of a map where clues come from, then search the area of overlap for your quarry
Trying to locate a fugitive, a kidnapped captive, or a hidden villain's lair in a Police Procedural or action flick? If there's no obvious address among the available clues, there's always process-of-elimination to fall back upon: if you can pinpoint what region of the city/county/whatever the other clues must've come from, then highlight them in bright primary colors on a map, there's sure to be just one area where all those clues' possible origin-points overlap. Congratulations, you just found your perp/crime scene/abducted Love Interest, while looking properly-clever for the audience. The actual nature of the clues may vary considerably, from ambient urban sounds in the background of a ransom-demand phone call to the distribution of wildflowers and soils in a thousand-acre forest. In some cases, the Venn Diagram technique will pinpoint the exact spot sought; in others, it'll narrow down the search-area substantially, and a little on-scene deduction will finish off the job (e.g. noting which abandoned building a perp could enter and leave without being observed). A Truth in Television trope, as many Real Life manhunts do come down to such a geographic process of elimination. Displaying this process may involve use of The Big Board or String Theory.
- Sherlock Holmes does this trope entirely in his head, usually starting with the type of mud on the client's clothes, which allows him to identify where they came from.
- Averted in one Judge Dee story: a kidnapped man is certain he was being held in a mountain home, because the palanquin he was in was tilted most of the way. However, Tao Gan points out that as it was enclosed, the kidnappers could very well have spent a long time carrying the palanquin up and down a set of stairs in a much closer house in the city, occasionally telling each other that they were getting a bit close to the edge.
- On Bones, it's very common for trace evidence of soil, pollen, or insect remains to narrow a search down to a specific area of the countryside.
- All of the CSI Verse shows use this trope on a regular basis.
- In an episode of House when nothing was left to go on but the sequential failure of otherwise unrelated organs in the patient, Dr. House formed a 'foreign object' diagnosis and used an anatomical version of this method to target the present location of the culprit a toothpick.
- This is done frequently on Castle, when a background noise or some small detail on the floor or ceiling makes them narrow it down to (for instance) all the factory warehouses that are near the ocean within Manhattan. Used along with The Big Board.
- Used regularly on NCIS, usually combining physical evidence identified by Abby with additional leads gathered in the field.
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