As written on the download page of the neighborhood:
"Mountainside Valley's been known for its vast mountain ranges. Many sims from all over the world move to this seemingly quiet little town, seeking inspiration, love or a better life. Is it the mountains that attract the sims? Or the fresh air? Or maybe the friendly sims around town? Who knows what this place among the mountains, down in the valley has in store?"
- Mountainside Valley, HBG
- Shaer: "The Shaer's just moved to town after a very long plane ride. Now it's time for them to settle in. Are they going to make a home out of this place? Will Layla and Sarah fit in among their new colleagues at school? Can Nadia finally sit down and rest her feet?"
- Kurtin: "Violet loves to throw parties whenever she gets the chance. Grey wishes she doesn't and just wants to return home to a quiet place. It's not like their twins are any helpful in that matter."
- Treah: "The Treah's have been popping out kids whenever they get the chance. They try to make sure that the nest is never empty, but that can't go on forever."
- Rhein: "Deliah decided to move after her husband died in a house fire. She wants to start a new life in Mountainside Valley and dreams of being a grandmother. Unfortunately all of her triplets are busy with other things. Especially Sheila, she still can't get over her father's sudden death."
- James: "When Mary met Danny, she knew that he would be her future husband. They're happily married now and already have two children. Mary loves her children and husband but it's time for Danny to get off the couch and get a job."
- McCormick: "Jules and Virginia never expected that Ryan would run away someday. They have no idea where he went and are worried sick about him. Will he ever come back?"
- Roomies: "Stuart was surprised when his nephew knocked on the door and begged for an accommodation. Craig and Robin wouldn't mind it so they have welcomed him in. Stuart is a bit doubtful, though."