This is the second English cozy for middle grade readers I've read set in a country spa! But in this one, Aggie and Hector go with her Grandma and mom, a widow, and governess on Christmas holiday to get away from death (yeah, not gonna happen) and promptly learn a woman, a previous client at the spa, died on a park bench.

Was the woman's death natural? Or was it murder? How will Aggie and Hector ever figure it out? 

Then a second client of the spa is found dead…on the same park bench, a Mr. Hart. The spa's doctor responds to the scene and dismisses it as a natural death. Mr. Hart had a bad heart.

It seems like case closed. 

Except Aggie and Hector quickly make an ally in the local undertaker's daughter, who's chafing at how -- simply because she's a girl -- she's restricted from learning medicine and applying those concepts to death, specifically homicide investigations. She's run a basic analysis of the first victim's hair and it definitively shows…da-dum! Signs of poisoning, over a long period of time. 

Ah, the sweet, sweet smell of mystery!

Once foul play is confirmed, it's a matter of Aggie and Hector figuring out who had a motive to kill both people -- Mr. Hart and the woman. They were both clients of the spa. As is Aggie's mom!

I can't say any more, or I'll ruin the mystery. Enjoy!