This episode is one of my favouries of the series. Sure, many people in the Star Trek and Sci-Fi universe have been over-run by an artefact of some kind and had multiple personalities in their head, but could anyone else have pulled it off better than Brent Spiner? His portrayel of many personalities in Data was just brilliant. The investigation of what was happening to Data and the artefacts being beamed onto the Enterprise was a great story too; trying to link the two events occuring. Even how some personalities in Data recognised some of the crew as enemies, leaders or comrads. A different type of episode for a story done many times in many TV shows.