The Doctor attempts to modify himself by adding behavioral subroutines while the Voyager crew treats with the Mikhal Travelers, trading supplies for information on the Nekrit Expanse. But while the Travelers seem very helpful, and Kes becomes romantically involved with one of their pilots, a strange series of changes begins to take place in the Doctor. The new subroutines seem to have created an alter ego which is becoming separate from the Doctor's normal personality. He begins to display a violent jealousy over Kes' blossoming relationship, combined with the ruthlessness to carry out his intentions. B'ellana's efforts to help modify his program only brings the ship, crew, and especially Kes closer to danger.
