The closed circle this time is the (small) passenger complement of a cargo ship. Alleyn is not fortuitously on board this time - he is assigned to the case, and knows that one of the highly individual 'types' is responsible for the serial murders of a number of women. I fairly early on discovered the connection between these women - they all have gem names. Eventually it comes out that the murderer is - as usual with Marsh - not the least likely but the least likeable character, a grumpy little man called, inevitably, Mr. Merryman. I liked some of the other suspect-characters - the Young Couple (doctor & recently jilted lass), and a priest (Anglo-Catholic) whose personality suggested that renunciation didn't come naturally. Alleyn's as charismatic as ever, of course. There's a quite dramatic 're-staging' at the end.