Rhianna's lifeless body lies splayed atop a salt spire on the south shore of Mono Lake. A sapling oak rises from inside the young woman's abdomen. Murder by tree hugger? Or something more complicated? On the eve of his arrest, the confessed killer walks up to an aspen tree and disappears into it. Heed is his name. A genetic interloper between flora and fauna. A shape shifter. Thus begins the mystery confronting Rhianna's ex-husband Marlyn, a transgender man, to uncover how a murderer could take the life of his beloved, and how he can bring himself to rationalize those same choices as his own.