Sixteen-year-old Sabine Braxton doesn't have much in common with her identical twin, Blythe. When their father dies from an unexpected illness, each copes with the loss in her own way--Sabine by "poeting" (an uncontrollable quirk of bursting into poetry at inappropriate moments) and Blythe by obsessing over getting into MIT, their father's alma mater. Neither can offer each other much support . . . at least not until their emotionally detached mother moves them into a ramshackle Bay Area mansion owned by a stranger named Charlie.

Soon, the sisters unite in a mission to figure out who Charlie is and why he seems to know everything about them. They make a life-changing discovery: their parents were hiding secrets about their sexual identities. The revelation unravels Sabine's world, while practical Blythe seems to take everything in stride. Once again at odds with her sister, Sabine chooses to learn all she can about the father she never knew. Ultimately, she must decide if she can embrace his last wish for a family legacy--even if it means accepting a new idea of what it means to be a family.