Our hamster's death wasn't just a tragedy; it ripped open my world and exposed my wife's secret affair.

After six months away on a work assignment, a doctor returns home to find his pet hamster dead. He decides to preserve it as a specimen, but during the dissection he freezes: the hamster's lungs are completely black, the result of prolonged secondhand smoke. Neither he nor his wife, Lily Evans, smokes. Who, then, has been living in his home for the past six months?

He does not want to suspect Lily, yet the wallpaper behind the sofa has been quietly replaced, erasing the pen mark he remembered. A forum of strangers urges him to test her, and when he reaches for her hand she flinches before clasping it again. At the parking garage, Lucas Hayes, an intern from his hospital, greets them both and keeps flashing a watch identical to his own.

Digging deeper, he finds his unpublished research paper opened and copied. In two months a major surgery will be broadcast internationally, and he understands what they intend. His mother-in-law, Mrs. Evans, is scheduled for an elective procedure, and Lily insists that only he can perform it.