Returning from an off-world mission in a puddle jumper, Sheppard, Teyla, Ronan and McKay suddenly find themselves in a ship that swings wildly between complete power failure and power surges that are blowing out some of the ship's systems. When they manage to get back to Atlantis, a diagnostics check reveals no problem whatsoever with the jumper. Soon however, systems across the city are affected in the same way. McKay is having difficulty isolating the source but it finds him by shutting down all but his computer. When he finally manages to communicate with it, he and everyone else is in shock at who it claims to be.