As the Athosians and the Atlantis team get acquainted with one another and their new home, Dr. Carson Beckett tests a new gene therapy on Dr. Rodney McKay. If successful, this therapy will manipulate McKay's DNA and give him the Ancient gene needed for Ancient Technology Activation (ATA). This would mean that all personnel would be able to use the Ancient technology that pervades Atlantis. McKay already has a little device he's itching to use.

That night, though frightened by stories that "ghosts of the ancestors" still live in Atlantis, two young Athosians, Jinto and Wex, sneak out of their quarters to play hide and seek inside a cargo hold. Later, Sheppard is awakened by Jinto's father, Halling: Jinto has vanished.

During the search for Jinto, Sheppard encounters an inexplicable entity. It seems to be attracted to energy sources and feeds off of them. Over Atlantis' communication system, Jinto is heard yelling for help. He guides Weir and company to a panel in what looks like a closet, on the wall of which is a lighted map of Atlantis. McKay points out the spot where the most recent energy surge was detected. Sheppard touches it and a panel slides opens leading McKay and Sheppard into the same room in which Jinto and Wex were playing. The "closet" seems to be an inter-city transportation device. They find both Jinto and one of the Ancients' research labs.

I wonder if Dr. McKay learns to keep his hands in his pockets with all that Ancient technology laying around?  After enhancing his ATA gene, the one that controls the Ancient Technology, he turns on a personal sheild, but he is unable to get it to turn off.

He jumps over railings and even gets shot and doesn't get hurt.  He also cannot eat or drink.  And for some reason he has a problem with that.  Although I do think he could go to lose a few pounds.

The shield generator comes in handy when a black shadowy entity gets loose on in the city, and in order to get rid of it, they draw it to the gate.  When a generator being used as bait does't make it through the gate, the Dr. uses the shield to throw it the rest of the way through.   The entity then follows on the way to barren planet M4X-337.