I could not work out how Charlie knew to collect the keys left in the envelope under the pot at the front door so that he could go and plant evidence in Aidan‘s flat. I have re-read and reread and only can assume that when Tess said she had made all arrangements, she had actually called Charlie and left him the envelope with Aidan‘s keys to go to his flat and plant the evidence. Otherwise I enjoyed the book but as usual with Nikki French, there’s always a few ambiguities.