A bystander’s reaction to a theft following a foot-in-the door (FITD) technique was observed in a field setting. An experiment was conducted in the pavement area of a bar where a first male confederate was seated alone with his suitcase on the ground. In the FITD condition, the confederate asked a participant for the time, thanked him/her, and left to go into the bar. In the control condition, no initial verbal contact was displayed, and the confederate just left to go into the bar. About 20 seconds after the first confederate had left to go into the bar, a second male confederate arrived, looked carefully around him, took the first confederate’s suitcase, and then left the place. More participants intervened in the FITD condition to stop the theft (84 per cent) than in the control condition (47 per cent). Social responsibility activation was used to explain these results, which has significant implications for encouraging public involvement in crime prevention.