On the day that Thomas attends his grandmother's funeral, he discovers that he's inherited a strange box and meets a strange man who takes him to his grandmother's secret garden, where she grew weird and exotic plants. When someone tries to steal the box that same night, Thomas becomes entangled with the Guild of Magical Herbalists, a group of seven men and women, each with their own box through which they access gardens where they grow poisons, medicines, perfumes and other, weirder things. Thomas's grandmother was a member of the Guild and as Thomas becomes more embroiled with their activities, he discovers that his grandmother was murdered. And she is not the only victim - other members of the Guild begin to die. Thomas, together with Maud, the ward of Mrs Lawrence (another Guild member) must unravel who is committing the murders and why before they themselves become victims.
Singleton evokes a fine sense of the late Victorian period in this well-written historical fantasy. The story twists and turns as Thomas unravels the mystery but he remains a believable character, by turns frightened and fascinated by this new world he has uncovered. Maud, the girl who shares his adventures is mysterious and interesting, although I would have liked her to play a greater role in the events. The same can be said for each of the Guild Members - each is well drawn for the limited time they spend on the page, but I couldn't help but wish that the book was longer in order to give them more to do - particularly Hegel, the young German who owns the perfume garden, and Mrs Lawrence who owns the poison garden of the title.
My biggest criticism was with the unveiling of some critical items of backstory towards the end of the novel. Although again well-written, the structure for the revelations is such that it offers details that the narrator, Miss Hudson, could not possibly know. This is unlikely to be spotted by younger readers but may well be grating to older readers.
All in all, I would have preferred it had this novel been twice the size given the scope of the story. However, Singleton leaves open the possibility of a sequel and I would definitely be interested in reading more of Thomas's adventures.