The Cipher Garden

This is the 2nd of the Martin Edwards "Lake District" mystery series--see my previous post on the first one, The Coffin Trail, for a cast of characters. The cold case team, led by Hannah Scarlett, has received an anonymous letter saying that the wife of murder victim Warren Howe, was the killer, even though the case had never been solved. Hannah's sargent, Nick Lowther, was on the original investigating team, and grew up as friends with one of the potential suspects. He seems reluctant to re-open this particular cold case, so Hannah and one of the team's other detectives begin some initial inquiries.
Daniel is still intrigued by the apparent randomness of the garden layout for Tarn Cottage and has now figured out who the original owners were, so he's hot on the trail, hunting for information that will help him decipher the dead-end paths and odd plantings there. Hannah's partner, Marc, is helping Daniel look for material as he pursues his used book business. Miranda has had offers to write magazine columns but it will require her spending more time in London and Daniel is having doubts about whether she is really going to stick with their decision to leave their former lives mostly behind and stay in the small village of Brack. Daniel is still wanting to spend more time with Hannah, both for the insights she can possibly provide into Daniel's father, and also because he is attracted to her. His endeavors coincide with Hannah's investigation since the murder victim was half of a landscape/ garden design partnership, which is still functioning and is hired by Daniel to help him sort the garden. In the midst of everything, Daniel's sister Louise comes to stay after breaking up with her partner, and things get a little testy between her and Miranda.
Hannah is having some challenges of her own in both her personal and professional relationships. Nick is acting strange, and Marc is clearly annoyed at Hannah's continuing obsession with work. The case they have re-opened is a challenging one, not because of lack of suspects, but because there are too many, although they all seem to have alibis. The remaining Howe family--wife Tina and children Sam and Kirsty--, along with the wife of Howe's business partner, and the clients in whose garden Howe was killed are all in the mix. Again this is a twist you'll never see coming. The prologue as usual sets up expectations, but they will be the wrong ones as new facts come to light only very late in the book.