* SPOILERS *
Sheppard and his team come to a world looking for another team who hasn't reported back, but find that they've killed each other. They come across some Wraith technology which has the ability to affect the mind, causing you to see things that aren't really there. The DHD is destroyed and they have no way of contacting Atlantis!!
Ronan and Sheppard are trying to kill each other thinking the other is an enemy. The only one not affected by the device is Teyla and she's injured!!
I thought this episode was very adventurous and excited. I knew they were going to be OK in the end, but I still couldn't wait to see what happened next.