Some of Diana Lindstrom's fondest memories involve childhood experiments conducted under the watchful supervision of her Great-Aunt Nora, a celebrated physicist long ago shunned by the family for mysterious reasons.

Now in her adult years and a sought-after scientist herself, Diana learns that Nora is dying. She hires private-duty nurse Brooke Sheldon to care for Nora. Over the days and weeks spent in Nora's company, Diana and Brooke are privy to Nora's long-held secrets, along with her deep-seated regrets.

Trapped in a failing body, but with a keen mind, Nora Lindstrom watches as the spark of attraction between her great-niece and her caregiver grows into a flame. Determined to help the two younger women find the kind of deep love they so richly deserve, Nora makes a fateful decision that brings the past and the present directly onto a collision course. After all this time, it's still about chain reactions.