Katie O'Roark, who has received a heart transplant, is spending the summer at Jenny House to help others who face medical crises. She becomes a "Big Sister" to Amanda, an eleven-year-old with leukemia; Chelsea, a thirteen-year-old candidate for a heart transplant; and Lacey, a fifteen-year-old diabetic.

It's been a year since Katie, Chelsea, and Lacey spent a special summer at Jenny House. This time as Big Sisters to a new group of girls who are also facing life-threatening illnesses. When tragedy strikes Jenny House, the three best friends know that things can never be the same again.

Several months after being diagnosed as having a brain tumor, Cassie receives an anonymous letter and check. Can her sister Dani make Cassie's dream trip to Florida come true?