Final answer:
The theme of 'The Moustache' by Robert Cormier involves mistaken identity leading to a heartfelt moment of confession and forgiveness, illustrating themes of family, time, regret, and redemption.
Step-by-step explanation:
The theme of Robert Cormier's short story “The Moustache” revolves around the idea of mistaken identity and forgiveness as the central narrative unfolds. A simple physical feature like a moustache prompts a powerful emotional reconciliation when the protagonist, Mike, visits his grandmother in a nursing home. She mistakes him for her deceased husband because of the moustache, which leads to a heartfelt confession and forgiveness for past grievances. The story delves into themes of family dynamics, the passage of time, regret, and the chance for redemption and understanding.