This is the opportunity to be an "insider" into the process of one person's experience of working on a mathematical problem. The experience is enhanced through the support and intervention of a learning mentor who "knows" the learner. This mentor/learner dialogue is documented to describe the problem solving journey. It shows how the unexpected can lead both to uncertainty and a new approach which, in turn, can lead to new learning in mathematics. The teacher involved comes to a realisation that, in the classroom, the unexpected and the unfamiliar may lead to shutting down mathematical possibilities, rather than embracing the mathematical opportunities. (Contains 2 tables.)