This episode opens with a great sequence with SGC rescuing the people on Nassya from an attack by Death Gliders. However, while performing CPR on a dying man Carter is infected with a Goa'uld. SG1 doesn't realize the change in Carter until Cassandra (Katie Stuart) instinctively realizes that she is a Goa'uld. Don't worry though, it turns out that the Goa'uld within Carter is actually Jolinar of the Tok'Ra (a group devoted to fighting the Goa'uld oppressors). But Carter is still in grave danger, for there is a Goa'uld assassin on Earth that wants to kill Jolinar! The assassin is able to infiltrate SGC and attack Carter, leaving her and the Goa'uld on the verge of death. The assassin is captured and killed, but there seems to be no hope for Carter. Until, the Goa'uld within her gives up its own life to save hers.
For the most part, this episode has the feel of a "filler episode". The acting isn't note-worthy, and the plot itself is a little thin. However, this is the first introduction of the Tok'Ra, and there is a lot of action and some suspense. That being said, overall all it is a good episode.