6,500 suspects
One name is hidden in the master list. The clues eliminate the innocent until only one remains.
Case File CK-LDN-001 · London
THE CITY KILLERLONDON
A city-wide murder investigation built from thousands of suspects, locations and possible moments. Twenty-nine clues. One killer.
CASE OPEN · 2026
Evidence file / suspect dossier · London investigation
1,437 locations
Every location is treated by its full printed name — including the area or building detail after the comma.
1,200 possible times
Dates and times are eliminated independently until a single moment survives every clue.
Online evidence desk
Check your solution
Important: You do not need to type the answer perfectly. Start typing and select the matching entry from the official case list. If you make a small typo, the desk will suggest the closest match rather than marking you wrong.
Reference desk
Clue help
The book deliberately gives no shortcut order. These explanations clarify exactly how each clue should be applied without turning the investigation into a list of answers.
Detective’s notes
Tips
Keep them together
Some clues eliminate suspects, some locations and some times. Keep all three lists within reach and return to each one repeatedly.
Slow down at comparisons
When a clue links two lists, hold the relevant shortlists side by side and test the relationship directly.
Use the whole entry
For location clues, count against the complete printed entry — venue plus everything after the comma — not the venue name alone.
Frequently asked questions
Case notes
Do I have to type the answer exactly?
No. The checker uses the case’s official entries. Select the suggested canonical entry, or use the typo suggestion if you mistype it. This avoids penalising spelling while keeping the answer unambiguous.
Why does the location need the full printed name?
Because the book defines a location’s “printed name” as the entire line in the location list, including the venue and anything printed after the comma.
Can I submit only one of the three answers?
You can enter them one at a time while working, but the official result is based on WHO, WHERE and WHEN together.
Is there one clue that gives away the answer?
No. The investigation is designed so that all twenty-nine clues are needed and no single clue, or small handful of clues, gets you close by itself.
Series archive
Case files
London is the first file. As the series grows, each city will become its own investigation.
London
6,500 suspects. 1,437 locations. 1,200 possible times. 29 clues.
CASE OPENNew York
Case file sealed. Investigation not yet released.
Paris
Case file sealed. Investigation not yet released.
Tokyo
Case file sealed. Investigation not yet released.
The next case
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