This chapter examines the possibilities of the ‘bystander intervention model’ to explore the decision making of health and social care professionals when detecting and attempting to prevent financial elder abuse. It is often suggested that the cases that come to the attention of professionals represent the ‘tip of the iceberg’. If this is the case, argue M Gilhooly, Cairns, Davies, K Gilhooly and Harries, at various points in the decision making process professionals must be deciding not to intervene. Although this UK study goes some way to explaining why professionals find it difficult to detect financial elder abuse, or fail to act when they suspect such abuse, the study also revealed that many professionals do play safe and act even when in doubt. The finding that ‘mental capacity’ was a key determinant of both certainty that abuse was taking place, and likelihood of intervention, is concerning. Prevention requires that such abuse is detected well before an older person loses mental capacity.