A Pound of Cure by Lester del Rey

Henry's life is unraveling: his wife, Maryl, is struggling with the grief of never having more children and the absence of their son, Jimmy, staying with his grandmother. Desperate, Henry resorts to a drastic measure, substituting Jimmy with a robot twin while the real boy recovers from an accident.

Maryl’s acceptance of the fake Jimmy brings temporary relief, but as the lines between reality and illusion blur, Henry's decision spirals into a haunting exploration of love, deception, and the pursuit of happiness. What will become of a family built on such a fragile foundation?