Disappearances in the Mediterranean (Mathematics Professor Alfred Dunningham, PhD, #2)

One passenger on a cruise in the Mediterranean Sea is disappearing after each day in port; there seems to be connection between the four of them. Cruise line security is beefed up, and Interpol is brought on board to investigate. Nothing unusual is found, although one of the investigators thinks he's found a mathematical connection. Professor Alfred Dunningham, in Paris at a math symposium, is toasted for his work in solving the Famous Sites Murders in Sydney, Australia. His phone rings, an...