This week's Nikita marks the third appearance of my least favorite character: foreign dignitary/Michael's baby mama/MI6 agent/Gogol mole Cassandra (Helena Mattsson). Unlike the first two, though, this one's pretty good.

The episode opens in London, where Cassandra is meeting Ari (Peter Outerbridge). He's handing her a new assignment that seems to momentarily throw her. Alex clues Michael and Nikita into the fact that Cassandra is a mole, causing Michael to blow a gasket. He breaks stuff and then decides to get his son back. (Wouldn't Shane West be awesome if he was in a movie like, say, Taken?) Nikita says that maybe he ought to start with just confronting Cassandra rather than committing kidnapping.

Cut to MI6 headquarters in London (hey, graphics people? There's no hyphen in the official title of the agency), where Cassandra gets dispatched to Moscow to "teach Gogol a lesson." Who's in Moscow? Alex and Sean, who are surprised when Sergei Semak himself shows up at their door, looking for help to find Alex's mother. Alex believes that Semak is genuine, and makes an emotional plea on TV to her mother.

Meanwhile, Cassandra spots Nikita on an MI6 surveillance feed, and the two briefly brawl before an angry Michael puts a stop to it, confronting her with the knowledge that she's a double agent. She gives him a whole sob story about how she was approached to be a Gogol agent as a desperate teenager, and how she thinks she's going to leave Gogol and retire from MI6. On a spy show, that's usually the equivalent of painting a target on your back. Thanks to this conversation, Michael soon realizes that the whole thing is a frame job; another agent is waking into a trap so MI6 can be framed for Semak's murder.

Naturally this can't be allowed to happen, and so Nikita and Michael intervene, dispatching the Gogol henchmen and saving the life of the MI6 agent. When Ari pulls Semak out into the alley to be killed, he realizes his henchman is dead and decides he's just going to have to do his own dirty work. A few shots later, the much talked-about Sergei Semak is no longer with us. Ari does a pretty decent job of selling his cover story to the various lackeys in the office.

Michael and Nikita are reunited with Alex and Sean, and Alex tells everyone that she received a coded message from her mother, just before Ari phones to tell her that Semak is dead. Michael knows something is wrong, and he and Nikita go to help Cassandra's MI6 team out of a Gogol ambush. Unfortunately for them, they left one survivor, who tells Ari that they're in town. Ari immediately suspects Cassandra of turning sides again, and decides to leak her file to MI6.