The Key to a Killer by Olivia Blacke

Item: The Key to a Killer
Rating: 3
Author: BaronessMom

Posted November 10, 2026 by BaronessMom in Mystery, Review / 0 Comments

I voluntarily reviewed an Advance Reader Copy from NetGalley. This does not affect my opinion of the book or the content of my review.

The Key to a Killer

by Olivia Blacke

Series: Ruby and Cordelia Mysteries #3
Series Rating:

Published by Minotaur Books on October 20, 2026
Setting: Boston, Massachusetts
Genres: Cozy Paranormal Mystery
Pages: 368
Length: 10 hours and 16 minutes
Format: Audible Audiobook, Hardcover, Kindle
Source: NetGalley
Goodreads
Get Your Copy at: Amazon
Also in this series: Death at the Door

A woman and her ghost roommate investigate their most personal case yet in Olivia Blacke’s The Key to a Killer, the next book in the Anthony Award-winning Ruby and Cordelia Mysteries.

When Ruby Young discovered that her Boston apartment was haunted, she did what any reasonable person would do: befriend the ghost. Their relationship overcame a shaky start—Cordelia Graves never wanted a roommate in life; she certainly didn’t want one in death. After working together to solve a few murders, the two are close friends, but there’s a lingering question neither of them have been able to answer: what led to Cordelia’s death?

Lately, things have been adding up that suggest foul play. And when Cordelia’s memories of that day start to come back, the roommates can’t ignore it anymore: Cordelia was murdered. Ruby and Cordelia are going to have to piece together what Cordelia’s final days looked like—otherwise a killer could go free.

The Key to a Killer by Olivia Blacke has a good mystery with some redeeming characters.

Will Ruby and Cordelia figure out what happened to Cordelia?

Cordelia

Cordelia is a ghost. She can’t remember how she died or what she was doing that day. It is believed that she committed suicide. The only problem is no one who knew her really believed that. Cordelia has a ghost friend that helps her out once in a while.

I didn’t really care for Cordelia. Even though she tries to protect Ruby, she also puts her in harm’s way quite often. She comes across as caring and such, but her moral compass is a bit off. However, she is funny at times, and her memory does mean she is learning more about herself.

Another thing is she hasn’t figured out her ghost powers. In fact, the rules governing her spirit seem sort of strange. Yet, they added a nice touch to the story.

Ruby

Our human sleuth is Ruby. Ruby moved into Cordelia’s apartment and also took Cordelia’s job as office manager at the same tech company. Even though Ruby never met Cordelia in person, she has been living with the ghost for the past few months. Cordelia does help Ruby and is teaching her to cook. Ruby is loyal to Cordelia. They’ve found ways to communicate since Ruby can’t hear Cordelia.

I like Ruby, but I think she lets people take advantage of her. I think she is attracted to Cordelia’s brother, and I am not sure if that is a good thing. She is still young, but she is making her own way in Boston.

The Mystery

We follow Ruby and Cordelia as they unravel Cordelia’s last few days. Ruby actually confronts people that they have deemed as suspects. We really get a look at the type of person that Cordelia was in life. There are a few red herrings, and the actual culprit isn’t someone that any of us would have thought. That one was well played, Ms. Blacke.

I enjoyed the mystery part of the story and the way that Ruby covered for Cordelia.

Three Stars

My rating for The Key to a Killer by Olivia Blacke is three stars. While the mystery part was really good, I didn’t care for the characters. Also, the whole paranormal part is very different than most books that I’ve read with ghosts. If you are looking for a different paranormal vibe, you may enjoy this one.

Ruby and Cordelia Mysteries

Thank you for dropping by! I hope you enjoyed this review of The Key to a Killer by Olivia Blacke.

Until the next time,

Baroness’ Book Trove is an Amazon affiliate, which means that if you purchase something from Amazon, this blog receives a tiny percentage of the sale. This helps with the cost of the website and a few giveaways.

About Olivia Blacke

Mysterious, Spooky, Cozy & Kooky! Olivia Blacke (she/her) is the Anthony Award-winning author of the Ruby and Cordelia Mysteries, as well as the cozy Record Shop Mysteries and the Brooklyn Murder Mysteries. She had her first ghost encounter when she was five, but wasn’t involved with an active crime scene until much later, when she accidentally stepped into a chalk outline on a Manhattan sidewalk. Armed with a Criminology degree, she channels her love of the supernatural and passion for writing into darkly humorous supernatural mysteries. She wants to be a unicorn when she grows up.

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