The story depends on a made-up fact that some people, instead of having a blood type of "positive" or "negative," are neither. The term they used for this was "Rhesus zero," which doesn't really exist.
The movie starts with an Ambassador being gunned down in Argentina and then a cardinal in Holland... but when a robot is arrested immediately after that, one detective tells another that Interpol reports that a cardinal was gunned down in Argentina and an ambassador in Holland.... reversing the order.... hardly the sign of a good detective....