Allegra Geller (Jennifer Jason Leigh) is one of the best virtual reality game designers and creators in the world. She is testing the latest virtual reality game she has invented, eXistenZ, with a trial group. During the demonstration Geller is attacked by an obsessed hit man with a strange gun made of organic material that he managed to get past security. She is scared that there might be further attacks so she runs away, with PR trainee Ted Pikul (Jude Law) as her bodyguard. However, the only copy of the new game that Geller has is damaged as they escape. The only way to find out if it is still working is for Pikul to use a bio-port in his own body and help her play the game. The line between reality and virtual reality begins to blur as the world of the game begins to infringe on real life.