Shiver opens as one of our narrators, Grace, remembers the time she was bitten by wolves and almost killed. The way she remembers it, it was almost pleasant, though. Like being licked by a friendly dog. But bloodier. Her P.O.V. alternates with Sam’s, who is a werewolf when it's cold and a human when it's warm. Grace, the human, is in love with Sam, the wolf. In fact, she loves him before she even knows he comes in human form, too.
After a high school student named Jack Culpeper is killed by wolves, hunters invade the Boundary Wood to hunt the wolves. Sam is shot. Grace finds him bleeding on her deck... in human form! And naked! Cue wolf howl. Grace realizes that Sam is the wolf she’s been loving all this time because they share the same yellow eyes.
Over the coming weeks, Grace and Sam's love grows. Grace also learns more and more about the wolf world and is determined to find a cure for Sam before he becomes a wolf forever.
Meanwhile, Isabel Culpeper, Jack's sister, has discovered that Jack is still alive, and he's a wolf. Jack was kind of a jerk as a human, and he's even more of a jerk as a wolf. He's the most annoying animal since Honey Badger. Anyway, Isabel is desperate for a cure, too.
To increase the drama, a she-wolf named Shelby attacks Grace, but Sam fights her and Grace's dad shoots her. But Shelby lives to howl again another day. Shelby is one tough cookie.
When Grace and Sam are apart, Sam spends his days searching for Jack. He's afraid that Jack will expose the wolves's secret to the world. On top of that, Sam grapples with the fact that Beck, the man who turned him into a wolf in the first place, did it on purpose. By biting him, silly, not with Gamma Rays. Also, Sam is angry with Beck because Beck's kidnapped three people and has turned them into wolves. When Sam finds out that the people volunteered for it though, he forgives Beck.
Eventually, Jack gets desperate enough to trap Sam and kidnap Grace, demanding to know the cure. Grace never changed after being bitten, and he believes she knows the cure. Isabel hypothesizes that when Grace got sick, the crazy high fever she got right afterward killed the wolf virus. To induce fever, Isabel takes a blood sample from a man with meningitis and plans to inject it into Jack, Sam, and Grace's friend Olivia, who has been bitten by Jack. Don't try this at home, wolf cubs.
Olivia refuses the cure, partially because she's afraid, but also because she kind of wants to be a wolf. Jack and Sam are injected, but Sam changes into a wolf in the middle of the injection and runs away. Three days later, Jack dies.
Isabel and Grace hang out more, as Isabel mourns Jack and Grace fears Sam for dead. One cold night, however, Grace is refilling the bird feeder in her snowy backyard when Sam emerges from the woods. Not because he's hoping to crunch a yummy bird in his wolf jaws. No, he is human. They embrace and speak each other's name.