Passage Summary: Someone stole three million dollars, and we know the suspects are all former employees of the Treasurer's Office. Since some people on the mayor's staff used to work there too, some of them must be the suspects.

Conclusion: Some members of the mayor's staff are suspects in the theft.

Reasoning: All the suspects are former employees of the Treasurer's Office, and some of the mayor's staff are also former employees of that office.

Analysis: This is a classic 'undistributed middle' fallacy. Just because Group A (suspects) and Group B (some mayor's staff) both belong to Group C (former employees) doesn't mean Group A and Group B overlap. To demonstrate this flaw, look for an answer choice that follows the same 'A is C, B is C, therefore A is B' logic but results in a clearly ridiculous conclusion, like 'All dogs are mammals, and some cats are mammals, so some cats are dogs.'