Is eternal life a blessing or a curse? That is the question young Winnie Foster must answer when she discovers a mysterious spring on her family's property. Its waters grant immortality, and the Tuck family, who have drunk from it, tell Winnie of their experiences watching life pass by without ever growing older. But Winnie must decide whether to keep the Tucks' secret and join them on their never-ending journey, or to keep her mortality and remain in the world she knows. With a decision this life-altering, Winnie must consider the consequences of both paths and decide which is the right one for her.