She Walks Alone — Helen McCloy

A woman dies by violence aboard the Santa Cristina. A radio flash from the West Indies brings word of an apparently related death. A man's body turns up, and in his hand is a suicide note written in one woman's handwriting but signed with another woman's name.

But what part does the jar of blood play - and why is everyone so interested in the contents of a certain package wrapped in cherub-bedecked paper? That's the puzzle Captain Urizar has to solve in a case with a startling showdown.