J. J. Connington 
Two Ticket Puzzle [EPUB ebook] 

The Two Ticket Puzzle, first published in 1930, is a traditional British murder mystery; the victim is killed by a gunshot aboard a local train; however, the autopsy reveals that the fatal bullets were of differing calibers. Several suspects are immediately evident: his wife’s lover, an employee with a grudge, and a young heiress. Police Superintendent Ross sets out to methodically solve the mystery based on a number of clues and pieces of evidence. J. J. Connington is a pen-name of Alfred Walter Stewart (1880-1947).