Molly Snow's sister Robin is a world-class runner who may even have a shot at the Olympics. Robin is getting ready for her next big race on the day Molly's life comes undone. Ever Robin's handmaiden (or so it sometimes seems), Molly wakes at dawn in order to follow her sister's running course as her one-member support team. However, when Robin informs Molly that she will be training in the afternoon instead, Molly refuses to accompany her. In the meantime, Molly heads off to the family-owned nursery business where she commands the greenhouse.

Molly is actually looking forward to a little time alone after work in the whimsical cottage she rents with Robin. She is feeling stressed about their house since their landlord is insisting they move out immediately. This day, Molly is bringing home an abandoned cat she has rescued, along with some languishing plants she also expects to lavish with tender loving care. Just as she's entering the house, her cell phone rings. A nurse informs her that Robin has had a running accident and is in the hospital but can't explain further. Molly assumes that Robin has had yet another of the fairly mundane problems she has encountered in the past while running, such as an ankle sprain. She is more focused on her new cat's needs and in taking a shower.

However, when she reaches the hospital, Molly is shocked to find that Robin's circumstances are much direr that she ever could have predicted. The doctor tells her that her sister has not only suffered a major heart attack and was revived by a Good Samaritan who gave her CPR, but that she hasn't awakened. He fears that Robin may have suffered brain damage. Molly is numb, even as she holds the unresponsive Robin's hand and sees that a ventilator is breathing for her. How can a young athlete suddenly have a heart attack?

When Robin and Molly's parents, Kathryn and Charlie, along with brother Chris are on the scene, the family struggles to cope with their uncertainty and grief. Their relationships, especially between Molly and her mother, are strained by the tension. Molly has always felt that Kathryn preferred Robin; now Kathryn repeatedly sends Molly away to work at the nursery instead of allowing her to stay and provide comfort. Chris, who has been having marital problems anyway, finds his relationship with his wife strengthened but then stressed in surprising ways.

As Robin continues to be unresponsive, Molly sets out on a mission to discover more about her sister. She succeeds in unraveling many of Robin's mysteries, but the answers to Molly's questions complicate the Snow family's emotional bonds even further. Molly hopes that her journalist friend Nick Dukette, who also happens to be Robin's ex-boyfriend, will be an emotional support for her instead of the media liability Kathryn expects him to be. Molly also meets the man who resuscitated Robin, a teacher named David. She and David bond over their shared guilt. Molly half-believes that if she had accompanied Robin on her run, Robin would be fine. David is nearly sure that if he had gotten to Robin faster, she would have revived. As the days go by and Robin's family faces ever more difficult decisions, they discover new strengths.

New York Times bestselling author Barbara Delinsky delivers once again in WHILE MY SISTER SLEEPS. While readers may find themselves feeling just a bit at a remove from the characters, the book's heart-tugging premise and complicated family relationships give it an authentic poignancy. In addition, audiences are likely to appreciate that Delinsky adds a note of intrigue with the unraveling of family secrets and resists tying up the plot too neatly.