A character foil is a person who contrasts with another character (usually the protagonist) in order to highlight various features of the main character's personality. In this short story, Mr. Martin is the protagonist. Mrs. Barrows' character is so strongly in opposition to that of Mr. Martin that this is the reason for the dilemma of the story: he cannot tolerate her and plans to "rub her out." Mrs. Barrows is loud, brash, obnoxious, pushy, aggressive. She has been hired by Mr. Fitweiler to work in the company where Mr. Martin works. He is head of the file department, a precise, strange, quiet, small man who likes everything organized and in its proper place. He rarely speaks and when he does so, it is precise and to the point. Mrs. Barrows on the other hand uses baseball phrases that rarely have anything to do with what she is talking about (Are you sitting in the catbird seat?). Mrs. Barrows has been secretly planning to overhaul Mr. Martin's entire department. Mr. Martin has been secretly planning to "rub out" Mrs. Barrows, but in the end, their personalities are the thing that work for them - against Mrs. Barrows but for Mr. Martin. He goes to her apartment, has a drink, smokes a cigarette -- totally out of character for him. He makes threats against their boss, Mr. Fitweiler. Totally out of character. Therefore, when Mrs. Barrows reports him to Fitweiler the next day, Fitweiler does not believe her - the loud, brassy, out-of-control woman - she must be having a mental breakdown! No way would Mr. Martin do those things. He has worked for the company for 22 years! Mr. Martin, in the end, becomes the ultimate foil to Mrs. Barrows.