"I am not a Consulting Detective," Gemma Doyle reluctantly tells 10-year-old Lauren Tierney, when the little girl comes to the Sherlock Holmes Bookshop and Emporium to beg Gemma to find her missing cat, Snowball. Gemma might not be able to follow the clues to find the cat, but her dog Violet follows her nose to locate the missing kitten in a neighbor's garden shed. Gemma and Violet proudly return Snowball to her grateful owner, and Gemma basks in praise for a job well done. But a few days later Lauren is back with ten dollars in hand, wanting to once again hire a consulting detective, and this time for a far bigger job: Her mother has been accused of murdering her garden club rival.
Sheila Tierney's garden, which everyone said was the one to beat for the West London Garden Club trophy, had been vandalized the night before the club's early summer tour. Sheila confronted her former friend and gardening partner Anna Wentworth in a towering rage, and the women nearly came to blows. Later that night, after having won the trophy for best garden, Anna is found murdered and Sheila Tierney is the police's prime suspect.
Despite herself, and despite the disapproval of her police detective boyfriend Ryan Ashburton, the game is once again afoot, and Gemma finds herself and Jayne Wilson using their powers of deduction to ponder yet another curious incident.