Frequently asked
questions.

A hand-packed murder-mystery case file delivered to your door. Each box contains clues, keepsakes, ciphers and mementos — like an Agatha Christie novel where you play Miss Marple. No conclusions are drawn; the puzzling and detection is up to you.

Some of our boxes contain herbs and spices used as period props (for example, An Inheritance of Murder includes a small quantity of turmeric and chai). Please contact us at <a href="mailto:hello@cosykiller.com">hello@cosykiller.com</a> before making a purchase if you have an allergy to any herbs or spices and we'll tell you exactly what's in the case.

Start with An Inheritance of Murder. It's our gentlest case, built for puzzle-minded beginners — Braille, letter-to-symbol substitutions and one-time cipher pads. The Curse of Humanrah is the next step up with knock codes, Vigenère and occasional folding. The Secret of Site Q sits in the middle — challenging but solvable. The Legend of Ching Shih and Murder at Marlborough House are our advanced cases — do them once you've worked one of the others.

Cosykiller is written mainly for adults, but families can participate together. A note of caution: Murder at Marlborough House is set in 1888 Whitechapel and contains graphic descriptions and period drug references — 18+ for that one.

It varies by case, but every box contains a cover letter from Fairhall & Brett Inheritance Recovery — the fictional investigators who brief you on the case — followed by the documents, photographs, ciphers, maps and personal effects collected during the investigation. Some cases include dried botanicals, spices, telegrams, theatre programmes and small physical objects. Each case is a complete story in a single box, with the final solution sealed inside. Nothing to download or sign into.

Between six and eleven hours, depending on the case, the number of players, and how much you like to re-read. Most people spread a case over two or three evenings. You can pause whenever you like — put the lid back on, come back next weekend. Nothing expires.

Both work well. Every case is designed to be solvable on your own — no mechanic depends on a second reader. That said, two to four players is where a case shines, because half the fun is arguing civilly about motive over a drink.

Each case comes with three sealed hint envelopes — open them in order when you get stuck. There's also an online community where other detectives swap ideas (link included with your order). If you'd rather not break a seal, email <a href="mailto:supersleuth@cosykiller.com">supersleuth@cosykiller.com</a> with your case number and the document you're stuck on and we'll help without spoiling.

Yes. At checkout you can enter a different shipping address; the receipt only goes to the billing email. If you'd like us to include a handwritten gift note, drop a line to <a href="mailto:hello@cosykiller.com">hello@cosykiller.com</a> with your order number and the message.

Checkout is handled by Stripe. We accept Visa, Mastercard, American Express, Apple Pay, Google Pay and Link. Your card details never touch our servers.

Worldwide. UK orders go by Royal Mail Tracked 48 (or 24, if you pick express). EU orders are VAT-inclusive under IOSS, so nothing extra is due on arrival. Rest-of-world orders may incur local customs duties — that's out of our hands and depends on your country.

We hand-pack every case, so allow up to three working days for your box to leave our workshop. After that: UK Standard 3–5 working days, UK Express 1–2, EU 5–10, rest of world 10–21.

First check against the contents list in the Fairhall & Brett letter at the front of the box. If something really is missing, email <a href="mailto:supersleuth@cosykiller.com">supersleuth@cosykiller.com</a> with your order number and we'll post the missing item out straight away.

Unopened cases can be returned within 14 days of delivery for a full refund, minus return postage. Once a case has been opened we can no longer accept a return — so much of the experience depends on the seals being intact and the documents being unread. If something turns up damaged, email us within 48 hours and we'll replace it.