In this second novel in the Sunday Philosophy Club, Isabel Dalhousie's niece, Cat (she of the unsuitable boyfriends) is invited to a wedding in Italy. This means that Isabel is left in charge of Cat's delicatessen - a task to which the redoutable moral philosopher proves more than equal. She is intrigued by the customers, of course, given her irrepressible tendency to take an interest in the business of others, and one man in particular attracts her attention. He is recovering from heart surgery - a heart transplant in fact - and when Isabel gets to know him a bit better he reveals an extraordinary aspect of being the recipient of another's heart. Isabel is drawn into an investigation of the facts behind the transplant, with disturbing results. Her enquiries take time, but not so much time as to prevent romantic entanglements, both for Isabel and her housekeeper, Grace. And as for chocolate - that proves to have some very interesting philosophical ramifications - at least in the mind of Isabel Dalhousie. Chocolate is a moral problem, it transpires - invoking questions of temptation and, of course, human weakness.
We are all weak when it comes to chocolate, Isabel decides - should we just accept the fact and get on with it?