Ten-year-old Lauren Tierney appears at the Sherlock Holmes Bookshop wanting to hire a detective: 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. Sheila confronted her former friend and gardening partner Anna Wentworth in a towering rage, and the women nearly came to blows. Later that night, Anna is found murdered and Sheila Tierney is the police's prime suspect. The game is once again afoot, and it's up to Gemma to find the truth.