This paper, delivered as a provocative keynote address to the Collaborative Action Research Network (CARN) conference in Manchester on 28th October 2023, explores the question if action research might have a sweet spot. A sweet spot is defined as an ideal location, area or combination of factors for a particular activity or purpose. It draws on the work of Edgar Schein who has argued that the essence of understanding and working with human systems is to focus on the process of how we relate rather than the structure of the relationship. Schein distinguished different levels of relationship and his framing of humble inquiry as a disposition and a skill -- a disposition of accessing one's ignorance in a given setting and a skill of collaborative conversation. The paper proposes that how collaborative relationships that are built, developed and sustained in action research through humble inquiry constitute its sweet spot.