The third Ruby and Cordelia Mystery lives up to the promise of the first two. The Key to the Killer finds Ruby Young determined to find out who murdered the ghost who haunts her small Boston apartment.

Cordelia Graves’s death was thought to be a suicide by most, but Ruby’s not convinced, and as Cordelia’s memories surrounding the fateful day start to return, she too becomes convinced her extreme alcohol intake that day did not include the pills found in her system.

There are enough suspects for them to investigate, starting with the owner of the tech company Cordy worked for, whose position Ruby now holds. Cordy had a years-long affair with him, but don’t forget his wife, and even several employees. Then there’s the reporter who found Cordy’s body. Along the way, there will be a resolution of sorts for Ruby’s relationship with the young man across the hall.

Helping Ruby is Ian Graves, Cordelia’s brother who made his first appearance at the end of book two, but rest assured if you haven’t read the first two you will be able to catch up here. However, Ruby and Cordy are a sprightly duo are worth reading if you haven’t. Throw Ian into the mix, just out of prison on parole, and you have all the ingredients for a quirky story with a dose of the supernatural.

Auntie M especially enjoys the things Cordelia uses to communicate with Ruby, who is learning to discern her presence. Several sets of magnetic fridge words are a big aide in that, as is Cordy’s ability to fry new tech near her, pass through walls, and generally disrupt any area when the need arises.

There will be real jeopardy for Ruby as her investigation continues to a surprising conclusion. A solid mix of suspense with a twist and two main characters who are both likable.