The team arrives at a planet paradise and upon being greeted Jack eats some pizza and unbeknown-st to him it means he is now married. It also means he is infected by nanites. The nanites attack his system and he starts to age rapidly along with the rest of the population. It's up to the rest of the team to try and find a cure not only for him but for everyone on the planet.
For me this is just a so so episode. Rapid aging episodes generally mean really bad aging makeup and just an overdone trite story. This is certainly the case here. There is nothing new here except for the Nanites that will become something much more later