Sarah Pearson was born January 16, 1961. She met Vic Pearson at Blake Holsey High when he returned a hairclip that she dropped on the ground, by accident, which her grandmother gave her.
She is Vaughn's mother.
In Season one, all that is really known about Sarah is that she was Victor's wife and Vaughn's mother and that she was killed in the accident at Pearadyne Industries. When Josie and Vaughn go back to 1977 for the first time, we learn that she is one of those sweet and innocent girls and Vic Pearson has a major crush on her.
Sarah Pearson does not appear back in the plotline until Season 3. Josie, in a dreamstate, sees Sarah give Vaughn a pendant when he was a baby and she tells him that she will give it to Victor for safekeeping until Vaughn needs it.
Sarah Pearson herself does not resurface until a strange capsole comes out of a vortex in the sky. When the Science Club investigates it and solves the way for it to reveal its secrets, it plays a hologram of Sarah telling Vaughn that she is safe and loves him. The message confirms that Sarah Pearson is still alive. This information is not shared with Victor.
When Corrine is forced to re-examine her memory of when she and Josie went back to 1987, she remembers a suppressed memory of Sarah Pearson convincing Victor to not abort the experiment which lead to the Pearadyne explosion. She told Victor that he would ruin all of her plans, before correcting herself by rephrasing to our plans, if the experiment was turned off. She disappeared after refusing to go into the safe bunker and erased Corrine's memory of the event after catching Corrine watching her and Victor debating. This makes it appear that she was the driving force behind the plans of Pearadyne, not Victor.
Later, when Josie and Vaughn go to 1977 for the second time, they discover that Sarah knew all along that Josie would bring a floating chi gong ball to the past and that Vic would steal it. She was just waiting for Vic to show the ball to her. She is not the sweet, innocent girl as we perceived in season 1.