Most murder mystery parties hand every guest a character and a script. A cold case party hands them a police file and asks them to close it. Here is how to run one that people talk about the next day.
A scripted party has a problem built in: one guest is secretly the murderer, and everyone else is waiting for a clue card to tell them so. The fun depends on how well your friends can act. A cold case party removes the acting. Nobody is guilty, nobody has lines to learn, and everyone has the same job: read the evidence and work out what really happened on the night. The quiet friend who reads carefully becomes as valuable as the loud one who likes to accuse people, and that changes the energy of the whole evening.
For a first party, start with something that can be finished in one evening. Our free case, Last Call at the Bluebird, takes a careful group about three hours and needs no account, so it is a good trial run before you spend anything. If your group already loves puzzles, The Harvest Ball is built for a crowd: four hundred witnesses, thirteen minutes, and one glass nobody touched. Read the case page beforehand, but not the documents. The host should be a player, not a game master.
Four to six is the sweet spot. Fewer than four and each person carries too many documents; more than six and some guests end up watching. If you have a bigger group, split them into two teams working the same case in different rooms and compare answers at the end. Competition between tables does more for a party than any prop.
You have two choices. Online, the host opens the case and starts a room with Play with friends; every guest joins with a code on their own phone, so no one is reading over a shoulder. On paper, every case comes as a printable PDF: print one document per page, spread the folders across the table and give each guest a pen. Paper parties feel more like a squad room; phone parties are easier to set up and nothing gets lost under the snacks. Either way, put a large sheet of paper in the middle of the table for the shared timeline.
First 20 minutes: food, drinks, and the reopening memo read aloud. It explains what the file is asking you to prove.
Next 60 minutes: split the seven folders between the guests. Police reports, forensics, witness statements, photographs, records, personal documents and press. Everyone pulls every time, name and number from their folder onto the shared timeline.
Next 45 minutes: the argument. Each guest names the suspect they trust least and the document that makes them suspicious. Someone else has to find a record that clears or confirms it.
Last 30 minutes: the vote. In an online room everyone votes in secret and the host reveals all the answers at once, which is the most dramatic moment of the night. The game asks one question, who did it, and the group gets one accusation: once it is submitted the case closes, right or wrong, and the solution file explains which documents prove it. So agree on the killer before anyone presses the button; if you like, have everyone also write down how and why on paper and compare it with the solution afterwards.
Print a few documents even if you play online; holding an autopsy report changes how people read it. Give each guest a different colored pen so you can see who added what to the timeline. Ban phones for anything except the case. And resist the urge to drop hints if you happen to spot the answer first. The point of a case with no hint envelope is that the group earns the solution.
When the case is closed, the solution file appears and walks through every document that convicts. Read it aloud. It is the second best part of the evening, because everyone gets to find out which line they read past. Then decide on the next case before people leave. A group that has solved one file together tends to want another.