Narcissistic, brash, and self-destructive Jimmy Shive-Overly thinks all relationships are doomed. Cynical, people-pleasing, and stubborn Gretchen Cutler knows that relationships aren't for her. So when they meet at a wedding, it's only natural that the two of them go home together.

When their aspiring scientist friend Barry's invention goes awry, best friends Shelby and Cyd gain the power to leap forward and backward in time whenever they want – and sometimes when they don't. Now, they experience the twists and turns of friendship and must decide between fixing mistakes in the past or catching a glimpse of the future. While Barry and his assistant, Naldo, try to figure out how to replicate time travel for themselves, Cyd and Shelby use their newfound power to navigate high school life and Shelby's mischievous twin brothers, Bret and Chet.