Those you never knew shared the world with you, cannot become extinct. That’s the paradox that brings together Niven and Amy. She’s combing the beach for treasure when he walks out buff-naked from the surf. She’s an orthopedic surgeon and sees a collection of best limbs and musculature she’s ever come across. He’s a descendant of Avendar explorers stranded on Earth eight thousand years ago. He’s suddenly not sure he wants to keep walking towards a woman he’d secretly monitored for fifteen years. But he must…because if he doesn’t she’d not live through the night because a predatory Siren wants her dead. And the man sent to keep Amy alive is the Siren’s betrothed.