Unto us a son is given / Donna Leon.

Count Falier was urging his Venetian son-in-law to investigate, and preferably intervene in, the seemingly innocent plan of the Count's best friend, the elderly Gonzalo Rodríguez de Tejada, to adopt a much younger man as his son. Under Italian inheritance laws this man would then be heir to Gonzalo's entire fortune, a prospect Gonzalo's friends find appalling. For his part, Brunetti wonders why the old man, a close family friend, can't be allowed his pleasure in peace. And yet, what seems innocent on the Venetian surface can cause tsunamis beneath. Gonzalo unexpectedly, and literally, drops dead on the street, and one of his friends just arrived in Venice for the memorial service, is strangled in her hotel room--having earlier sent Gonzalo an email saying "We are the only ones who know you cannot do this," referring to the adoption. Now with an urgent case to solve, Brunetti reluctantly untangles the long-hidden mystery in Gonzalo's life that ultimately led to murder--a resolution that brings him way more pain than satisfaction.