Cosykiller is an interactive murder mystery subscription box for the armchair sleuth

Plans as low as $36.67 / month
Product Overview
  • For UK - arrival 2-4 days. For USA: we ship in bulk on the 1st and 14th day of each month. USA boxes arrive within 7-10 days of that bulk shipment. All other territories items are shipped airmail as orders arrive: 14-21 days depending on destination. All boxes should reach their destination within 21 working days.
  • Ships worldwide from United Kingdom
  • Subscriptions automatically renew. Cancel anytime
Immerse yourself in the story and find the killer
Always fancied you could crack a cold case? Now you can find out with a Cosykiller subscription box. Each storyline lasts a year. The box is delivered directly to your door and packed with vintage memorabilia, keepsakes and intrigue. There are puzzles, ciphers, suspects, back stories and false leads. It's difficult and requires tenacity.
  • Work on your own or in a small "detective team" as the boxes arrive
  • Work at your own pace, or ask for hints from the private facebook group
  • Features vintage memorabilia, coherant storylines, replica items, keepsakes
  • Solve a murder from the comfort of your own armchair!
  • Each letter accompanying the box is personalized to the customer - which makes it a great gift item.



Q: If I start now, do I miss the first four months of the story? Asked by Annette S., April 2020

Hi Anette You start with box 1 whichever month you begin as the Cosykiller team keep an eye on the subscribers and always start people on box 1

by Joaane S., April 2020


Q: Can you start at any month? If I order late January will my box be the first box needed?Asked by Christi M., January 2020

You start with box 1 whichever month you begin as the Cosykiller team keep an eye on the subscribers and always start people on box 1

by Joaane S., January 2020


Q: We are looking at this for our family, what age range would you suggest this product for?Asked by Adam D., December 2019

I'd say teen and up - but it suits geeky teens rather than gung ho teens. They need to be into stories and puzzles and ciphers.

by Joaane S., December 2019


Q: Can you get just three boxes or do you have to purchase the full year to get anything out of it?Asked by Heather K., November 2019

You can buy however many boxes you like. There will be some puzzles you can solve in the first three, but there will be others (like the murder mystery) you wont be able to solve until you've had all 12. The story builds over the year. Year 2 - it's a totally different story - year 3 - a new story again!

by Joaane S., November 2019

Cosykiller reviewsReviews

Write a Review
7 reviews

CozyKiller is fun and entertaining

Apr 20, 2020
Chrissa C.
1 Review
Subscribed for 29 days

It’s my first time trying this kind of subscription. The objects that come with this box are amazing! The subject is interesting and there are a lot of things to learn and to explore with this mystery.

Verified Purchase

Love this!

Jul 08, 2019
Christina M.
1 Review
Subscribed for 4 days

I just got my first box and it is really cool. The journal came burned, it is so interesting. I wonder why, that is something I need to figure out. This is the best box ever!!!! If you like mystery, i highly recommend.

Verified Purchase

Murder, mystery, intrigue

Sep 05, 2018
Rebecca P.
1 Review
3 Helpful Votes

Cosy Killer is by far the best murder mystery subscription box. If you are looking for an engaging experience filled with authentic characters, a story with multiple interwoven plot lines, puzzles that are organically entwined within the narrative which serve to enhance the whole experience then this is it. The excellent skills of the CosyKiller team encourage an inevitable emotional investment in the characters. While you know that you are investigating the death and whereabouts of Marie, there is a point in Box 9 where you decode a tricky artifact, with every letter decoded my heart ached a little as I could predict what the next letter would be.

If you want an experience like no other I have encountered, one that will keep you puzzling and that keeps you coming back for more - then Cosy Killer is the only subscription box out there.

Treat yourself - you won't regret it

Varied, multi-puzzle, longform narrative

Aug 30, 2018
Craig J.
2 Reviews
3 Helpful Votes

Let's get the downside out of the way first - CosyKiller is a year-long subscription. Telling one story over twelve monthly boxes, it's some commitment of money and time.


What it gives you back for that subscription is unsurpassed in terms of mystery subscription boxes. There are no phone numbers to call that might end up disconnected after a few months, there are no websites to visit that might be taken offline at no notice, everything you need is there in the boxes.

And what boxes they are - one month you might get a 128 page diary/journal containing two obvious ciphers and one very well hidden one. You might get twelve to sixteen letters from one character to another, including drawings and birthday or christmas cards. You might get clay artifacts, or death certificates, or shipping manifests, or telegrams, or....

You can read something in box 8 that reminds you of something in box 1 to find an inconsistency in testimony that feeds into the final solution - you can find ciphers in early boxes that are made more explicit later on, but still solvable at that early stage.

The commitment is huge, but the project is major league, satisfying, intelligent, interesting and thoroughly recommended.


Aug 29, 2018
Lisa S.
2 Reviews
1 Helpful Vote

I am only three episodes in but the storyline is awesome and very gripping. I didn’t want to stop reading! You get very authentic items and they pay close attention to detail. Very impressed!

Good grief! They musta used the pages as

Jul 02, 2019
Stephanie A.
1 Review
1 Picture
Subscribed for 15 days

I haven’t started the storyline. The journal was burnt so bad it is all over my hands. Smells awful. I can’t even read the last pages. I’m going to contact the seller for a new journey that smells like Masela rather than paper used to light a fire. Sigh

Verified Purchase
Cosykiller said...Jul 02, 2019

Sorry you've not enjoyed your first box. The burned state of the journals are a deliberate ploy by the story writers to create an authentic experience.

A house fire is part of the story.

If you specifically don't like the authenticity of the burning - we can ship an unburned version to you from the UK (we receive them here unburned and spend hours burning them by hand to make them look and feel authentically like they've been through a house fire!)

A UK shipment of a replacement untainted copy will take around 10 -14 days to reach you as we have to ship them via airmail.

Let me know what you'd prefer. I can ship another burned copy from the USA...

Unique and Highly Immersive Subscription

Jun 07, 2019
Leslie S.
2 Reviews

I feel like I've been transported to 1930s India, and I'm only working through the journal in the first box! I cannot wait to see what's next! In addition to the game itself, the women who are Cosy Killer have been very welcoming and accommodating with all of my questions! Way to go, ladies! You all are fantastic!

Photos from reviews of Cosykiller

Past boxes from Cosykiller

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