ARC Review: The Key to a Killer by Olivia Blacke

The Key to a Killer
Author: Olivia Blacke
Series: The Ruby and Cordelia Mysteries (Book 3)
Publication: Minotaur Books (October 20, 2026)

Description: 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.

My Thoughts: In this third Ruby and Cordelia mystery the roommates and partners in detection are finally ready to solve the mystery of Cordelia's murder. The problem is that Cordelia doesn't remember her death or the day leading up to it.

Ruby, who works for the same company Cordelia worked for before her death, wonders if Cordelia's death stems from her long-time affair with her married boss or if it has something to do with some software the company claims was stolen by a rival company.

Cordelia is sure that her lover didn't kill her, but her surety is based on feelings and not evidence. But her lover isn't the only possible suspect. A strange man was seen leaving Cordelia's apartment on the day she died carrying a laptop case. Cordelia's laptop along with her wallet, phone, keys, and watch all were missing when her body was found. 

Then there is the reporter who discovered her body and who believed that Cordelia was going to blow the whistle on her company. That same reporter is working on an article about the statistically large number of burglaries in the apartment building. 

Both Ruby and Cordelia are investigating what happened when Cordelia died in their own way. Ruby has been befriended by a man who works for the rival software company, and she hopes to get some answers from him. Cordelia is also lurking around the company and blowing up anything electronic that she gets close to. 

This was an engaging mystery about two very unlikely friends and even less likely detectives. 

I received this one in exchange for an honest review from NetGalley. You can buy your copy here.