Mr. Monk Can't See a Thing - S5.E4

When Monk goes to his firehouse to get his smoke detectors inspected, the crew is quickly called away to a fatal house fire in which a young woman is killed. Minutes later, a mysterious intruder walks into the firehouse, lethally bludgeons a veteran fireman, blinds Monk with cleaning acid, then escapes. Despite Monk losing his eyesight, Stottlemeyer coaxes him to continue investigating, and Monk soon finds that the fire and his attack are connected.