The city of Atlantis goes into lockdown in a brand new episode, airing this Friday on SCI FI Channel in the U.S.! Now GateWorld has received new story details on Season Four’s thirteenth episode, “Quarantine.”

The episode will see at least one major relationship development for one of the show’s regular characters.

Here’s how SCI FI describes this week’s episode:

A nervous Dr. McKay arrives in the botany lab, prepared to pop the question and finally ask Katie to marry him when an alarm sounds throughout the city. A quarantine lockdown goes into effect, trapping them in the lab. McKay suspects that a highly infectious disease has triggered the city’s automatic self-protection system.

Other members of the expedition are faring no better. Lt. Colonel Sheppard and Teyla are trapped in McKay’s lab, Colonel Carter and Dr. Zelenka are confined in the transporter, and Dr. Keller and Ronon (Jason Momoa) are stuck in the infirmary. With communications and other vital systems affected, each believes the other will be coming to their rescue, unaware that they all share the same predicament.

“Quarantine” premieres Friday at 10 p.m. Eastern/Pacific on SCI FI, and Tuesday, January 22 on Sky One in the United Kingdom.

MGM has posted photos and a video teaser from the episode at their official Stargate Web site.

Learn more about upcoming episodes in GateWorld’s Season Four episode guide.