When Cassandra collapses at home, she is taken to the SGC for treatment. A retrovirus is causing her to emit an EM field and she expresses a need to return to her planet for an initiation ritual. SG-1 investigates and finds a Goa'uld laboratory, probably having belonged to Nirrti, meant for experimentation on the planet's population. They find that the ritual is part of the experiment, a time when Nirrti studies her subjects and cures them when she is done. SG-1 has found a way to cure Cassandra, but now all that remains to be found is Nirrti.