This paper describes how mystery shopping can be used to gain valuable strategic input in B2B service relationships. We account for a longitudinal case study framed as a natural experiment (duration 18 months) in a Swedish group of consultancy companies offering a wide selection of industrial services to large Scandinavian corporations. We account for and analyse the process of building a mystery shopping procedure to get strategic insights from engineers delivering temporary consultancy services to these clients. After a successful trial period with three mystery shoppers the experiment (a guideline covering the themes of map, smoke and mirror as metaphors) has been extended to comprise a larger group of engineers and may be taken up in a company-wide way. The experiment was deemed effective in developing both a procedure for mystery shopping and a new way to train the consultants.