Linda Ko

Plant samples brought back from a new planet introduce an amnesia-inducing virus that strikes everyone in the city except Teyla (Rachel Luttrell) and Ronon (Jason Momoa), who appear to be immune. Carter (Amanda Tapping) orders the Gate?s control crystal removed to stop the disease from spreading to other planets while Major Lorne (Kavan Smith) and his soldiers are given orders to control the Atlantis population with stun guns.The team discovers that a cure might be available among the plants on the mainland, so Ronon and Sheppard (Joe Flanigan), whose memory is also fading, set off to obtain it. Meanwhile, McKay (David Hewlett) works on a widespread distribution method but is unable to complete it before he too succumbs to the virus.When McKay wakes up, he is strapped to his desk in front of his console, with no idea who he is or what is going on. Following instructions from a video he recorded earlier, McKay frees himself and sets out to find Teyla (Rachel Luttrell), the key to unlocking this mystery. Also available on iTunes

While exploring a new planet, Sheppard started to watch a strange crystal. He doesn't know why, but he had to touch it. Back on Atlantis, everybody but him started to have some bad nightmares. Also available on iTunes

When Rodney McKay (David Hewlett) realizes Atlantis has started shutting down artificial gravity and collapsing protective shields to compensate for a damaged power system, he turns off all non-essential systems. But when the problem persists, McKay is forced to collapse the shield to the point where it is only protecting Atlantis' main tower, leaving the rest of the city exposed to space.With the protective shields down and an asteroid belt fast approaching, Lt. Col. Sheppard (Joe Flanigan) leads a group of Atlantis personnel on a desperate jumper mission to clear a path for the city. Meanwhile Dr. Keller's (Jewel Staite) attempts to resuscitate a comatose Elizabeth Weir (Torri Higginson) reveal that her patient has severe brain swelling and will require radical surgery. McKay runs the calculations and realizes there's an even bigger problem: in just 28 hours, the city's shields will fail completely and all of Atlantis' inhabitants will succumb the vacuum of space. Also available on iTunes