The Tok'ra and rebel Jaffa fighting along side them suffer heavy casualties when Anubis' forces overrun SG positions in the Risa system. During the funerals that follow, a scuffle breaks out between Ocker, a Tok'ra and Artok, a Jaffa. Meanwhile Carter discovers that someone has tampered with the Naquadah reactor. Realizing that a saboteur is on board, O'Neill shuts down the gate. When Ocker is found dead, Artok becomes the prime suspect and tensions between the two uneasy allies threaten to boil over. But an autopsy showing that Ocker and his symbiote had their spines severed from behind, not in a face-to-face encounter like those favoured by Jaffa, points to Artok’s innocence. Before he can be freed, Artok is found dead in his cell. There is no sign of resistance and no explanation of how the killer entered and exited Artok's cell. A riot is averted when Bratac finds the killers tracks and the group splits into search parties. One search party turns up dead. Then enemy attacks and kills Bratac. Teal’c and the other rebel Jaffa are furious with Malek for failing to help their leader, but he swears that Bratac was attacked by some invisible force. They realize that the killer is Nirrti, a highly trained gou’ald assassin equipped with a cloaking device. Carter alters the Naquadah reactor to produce an electromagnetic field that reveals their invisible foe. Nirrti quickly shuts off the reactor and begins killing everyone in the room. At the last second, a badly wounded Bratac reappears and kills Nirrti with a series of deadly staff blasts. Bratac and Malek make amends, bringing the Tok’ra and the rebel Jaffa closer together in their fight against the evil gou’ald empire.