Inspector Alleyn on the job once again in an enthralling story with an unusual setting and a new twist to an old pattern. The action, for the most part, takes place on a freighter, outward bound from the Pool of London. Murder has been committed on the dock:- it is the third in a sequence of identical factors -- the one new clue is the torn slip of an embarkation notice, suggesting that it was snatched from a passenger on the freighter. And so Alleyn, incognito, comes aboard from the pilot boat, his purpose a closeup study of an oddly assorted number of passengers, all of them suspects, and the prevention of another murder. The very tightness of the confines of the ship and the plausible shift of suspicion from individual to individual keeps the reader on tenterhooks until the dramatic finale.