CosyKiller: For the Armchair Sleuth

by Cosykiller
Crack the case with this interactive murder mystery subscription box.
11 reviews

Product Details

The Cases Are Cold. Your Trail Is Hot.

Ever wanted to solve a murder? This murder mystery experience brushes up your sleuthing skills while immersing you in a complex world of puzzles, ciphers, suspects, and backstories - there’s even a few false leads to throw you off the trail. Each box is packed with vintage memorabilia, keepsakes...and intrigue.

  • For ages teen and up; work on your own or in a small detective team of players
  • Monthly subscription; 1 mystery takes 12 months (12 boxes) to complete
  • Internet isn’t required but hints are available from a private Facebook group
  • Features vintage memorabilia, coherent storylines, replica items, and cool keepsakes
  • Each letter accompanying the box is personalized to the customer - makes it a great gift item!

Customer Questions (13)


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: How do I pay monthly?????? Will I get charged the 440$ upfront???? I want the whole year, but to pay monthly Asked by Dezeray D., December 2020

Cosykiller answered...December 2020

Hi Dezeray
When you go to payment it will give you the option of how you'd like to pay. Select monthly.
Thanks so much


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: I live in the US and see that you offer free shipping internationally. Will there be additional customs/duties fees for each box? If so, how much more expensive will this be?Asked by Chelsea S., February 2021

Cosykiller answered...February 2021

Hi Chelsea
We send our US boxes from our counterpart in the US, so you shouldn't incur any additional fees.
I hope this helps.

Reviews (11)


Jul 24, 2020
Verified Purchase
Natalie H.
1 Review
4 Helpful
Subscribed for 10 days

Eeeeekkk!! I love this box! What an excellent idea. I bought it as an activity my husband and I could do together during lockdown. We've only had the first box so far but we were so impressed with it. I was addicted to smelling the burned journal! It smells so wonderful and I can see how much effort has gone into preparing it. We loved deciphering the codes. The only thing we're sad about is that we have to wait so long for the next box! We're itching to continue the story. Well done for creating such a fun experience.

Murder, mystery, intrigue

Sep 03, 2018
Rebecca P.
1 Review
5 Helpful

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
7 Helpful

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.

CozyKiller is the best!

May 09, 2021
Verified Purchase
Jodee L.
1 Review
Subscribed for 15 days

My sister and I love love love cozy killer! We’ve tried four different mystery boxes and this one is by far the most engrossing and entertaining!

Love this!

Jul 08, 2019
Verified Purchase
Christina M.
1 Review
Subscribed for 2 months

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.

CozyKiller is fun and entertaining

Apr 20, 2020
Verified Purchase
Chrissa C.
1 Review
Subscribed for 4 months

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.


Dec 01, 2020
Verified Purchase
Brandy L.
2 Reviews
Subscribed for 20 days

There were no directions.


Aug 29, 2018
Lisa S.
2 Reviews
1 Helpful

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

Jun 27, 2019
Verified Purchase
Stephanie A.
1 Review
1 Picture
Subscribed for 3 months

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

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...

Worth it

Jul 25, 2020
Mya N.
3 Reviews

SOOOO much fun!

Photos from reviews of CosyKiller: For the Armchair Sleuth

Past boxes from CosyKiller: For the Armchair Sleuth

Shipping Policy
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...
Cancellation & Refund Policy

Cosykiller was featured in these articles…

Cosykiller appears in these collections...

Questions for Cosykiller?