In which Captain Martin Arrowsmith, burdened by weariness and doubt, makes an unexpected discovery about a mysterious principle in staphylococcus-infected pus that arrests bacterial growth, setting him upon a fervent path of rigorous experimentation and cautious hope. Yet this scientific triumph entangles him in relentless toil and creeping neurasthenia, undercut by the skeptical vigilance of his mentor and the fragile solace of his devoted wife.