Mr. Monk Can't See a Thing

S5 E4: When Monk stops by his local firehouse to have his smoke detectors inspected, a fire breaks out in a nearby home, calling away the fire company and leaving Monk alone with a retired fireman named Rusty. Soon thereafter, an unidentified man enters the firehouse. Rusty confronts the intruder, who hits Rusty over the head with a shovel. When Monk responds, the intruder throws solvent into Monk's eyes and makes his escape, leaving Rusty dead and Monk blind.