This case study is an inquiry about feedback in the context of professional development. It tells the story of the feedback process between a teacher and his colleague as they work with a group of adolescent science students. The entire process is reported in a day-to-day description of the interaction between the two men: (1) "Beginning the Process," (2) "Feedback Overload," (3) "Different Perspectives on Success," (4) "Being Explicit about the Process," (5) "Co-operative Planning," (6) "A Crisis with the Process," (7) "A Change in Tone Contributes to Co-operation," (8) "Returning to a Former Mode of Feedback," (9) More Talk about the Process," (10) "Boundaries of Discussion," (11) "Constructive Feedback Deteriorates," (12) "Co-operative Work," and (13) "Stress of the Process." (JD)