This was a very intriguing episode...up to the end.  The ending was very abrupt with the cruise director saying she is going to investigate.  SPOILER ALERT:  The steward will testify that he ABSOLUTELY was onboard ship, so why not say that the other gentleman didn't use his real name when he seduced her?  If it were I, I would have killed my wife and then killed my brother on the pretext that my brother had done the deed.  Murder mystery, no supernatural elements.