In a strange twist, McKay’s sister, an accomplished scientist and now a “stay at home” mother, may have found the solution to creating new ZPMs with out knowing it. But McKay’ sister, Jeannie, is reluctant to either assist the military, or help out her brother, whom she has not heard from for over four years.

However, once onboard, McKay and Jeannie put her theoretical physics formulae into practice. The problem is the process that will give them a new power source will also produce “dangerous exotic particles.” Jeannie’s theorem could allow for these dangerous exotic particles to be sent instead to a parallel universe; one that the odds are will be uninhabited, hence not endangering this universe.

During the start up test phase, they are surprised to receive the “McKay” from the parallel universe they are targeting. He tells them that the exotic particles being generated, are about to destroy his universe.

The team must find a way to fix this error, which could also endanger their own universe. At the same time, McKay must also put up with the nicer parallel version of himself, and also try to repair the tension that has existed between him and his sister.