Best friends are there for each other whenever one needs help. In the case of BFFs Shelby and Cyd, that `whenever' can be any era in history. After a science experiment goes awry, the teens acquire the ability to travel through time whenever they want and, sometimes, even when they don't. They try to use their recently acquired power to help navigate their teenage years, both in school and in their family relationships - especially when it comes to Shelby's mischievous twin brothers Bret and Chet - which often includes going back in time to fix past mistakes. And for some fun, the girls occasionally sneak into the future to get a glimpse of what's to come.