 Season three of Enterprise features an ongoing story following an attack on Earth by previously unknown aliens called the Xindi . In this episode , while investigating a planet visited by the Xindi , several crewmembers including Captain Jonathan Archer become infected with a virus that mutates them into another species . The crew of the Enterprise must prevent an alien race from exterminating the mutated crew @-@ members while developing a cure themselves . The episode was written by story editor André Bormanis and directed by Star Trek : The Next Generation alumnus LeVar Burton . 
