John Moss introduced his detective duo, David Morgan and Miranda Quin, in last year’s Still Waters. They were an appealing team, navigating the bounds of professional partnership and personal involvement, more prone to banter and introspection than active investigation. Now they return in a new adventure that has a sordid mix of gruesome death, gothic overtones, and ancient rites. But the end result resembles an undercooked pie, with fruit leaking out of the middle and edges  too soft to hold everything together.

The new book exacerbates the main weakness of Still Waters, which suffered from an uneven balance between horror and compassion. Here the inciting crime – the discovery of two colonial-garbed, embracing, headless corpses – is depicted in grisly detail, but Quin and Morgan’s subsequent interactions stem less from burning need to bring the killer to justice than from a desire to extend the arch dialogues that run between them.

Other characters arrive to complicate matters, but this often seems forced (one key character is named Alexander Pope, apparently without irony). The disconnect between believability and contrivance is never more apparent than in the way Moss depicts young police officer Rachel Naismith, employing Quin’s point of view to dwell on potential sexual tension between them. There’s little to prepare the reader for such an emphasis.

Grave Doubts, understandably, hangs its hat on Morgan and Quin, hoping that the strengths and quirks of these two characters, together and separately, will carry the momentum forward. But a baggy plot with inexplicable twists is simply too much for the novel to overcome. Moss’s previous books demonstrate he has the chops on a prose level, which is why the fruit, however soggy, is still tasty enough to eat. But a crime novel, like a pie, needs a solid structure that holds together in all the right places.