After the obliteration of Anubis' Fleet and his second huge "Mother" Mothership, there are all kinds of pieces of junk floating around in orbit. One of these almost hits what looks like the Mir space station. Anubis' First MegaMothership was destroyed over Laangara/Cowlonna - Anubis seemed to have a never ending supply of these ships which dwarf "regular" Motherships.
But debris is the least of our worries, inside this particular piece of junk was Anubis' "Ghost".
It was bad enough when Anubis had a body, now he can float around and take over anyone he wants to, shades of "The Hidden" - The only way to identify a "Host" that has been Anubis-Infected is to notice that it starts rotting away. But since it takes a while for this decay to begin, it is difficult to identify "Where's Waldo", especially when Anubis plays "Musical Bodies".
Fortunately, as with All Goa'Uld, they don't know the meaning of the word "Covert". Even after Anubis had driven Colonel Alexi Vaselov like one of those Blue guys from "Avatar" for a week, he does something to give himself away: He might have even convinced Jack to put him on SG-1, if he had not been so insistent. When he fails to get Gate Access inside of Vaselov's body, he gets into Daniel Jackson, who made it all the way to the Embarkation Room with an Open Stargate before he was found out.
So now it's "How do we get rid of unwanted Anubis Ghosts"? Well, mainly by "Gennel" Jack calling for a full Lockdown. Even after the great double intro episode for Season 7, and Jack's new Position as Brigadier Gennel, it was hard for me to swallow that "Jack is the Man" - And he has to stick it to himself because of a serious lack of Hammonds to stick it to.
The highlight of this episode it of course Director/Actor Gavin Hood as Russian Colonel Alexi Vaselov. Hood, who has taken over Direction of the Wolverine Sub-Franchise and also did Ender's Game, is a fine "Russian Colonel" in this episode. He is not just a "vessel" for Anubis, when he is acting as himself he is an honorable man, one of the rare honorable men who come and go into Stargate/Homeworld Command, as opposed to the Kinseys and the Maybournes of the past.
This is also the first appearance of Dr. Brightman as played by Alisen Down, look for her as an "Alteran" in "The Ark of Truth". She was Brightman again in four episodes of Stargate Universe.
After SG-1 plays hide and seek with Anubis, it took a great sacrifice by Hood/Vaselov to get him out of Stargate Command. The story of Anubis is eventually dealt with in "The Reckoning" and "Threads" - Suffice it to say here, he is almost a worse threat than before, he can't be killed. And if he takes a host, it's goodbye host, unless he is chased out. But Vaselov is able to stop him, at least for now.