In your answer, you'll want to briefly summarize the situation ("A client's product needed to be recalled."). Then, talk about what you did ("We had a strategy on hand for this kind of situation, which we modified to fit the circumstances. We had a conference call with the client, who was initially reluctant to make statements online. We explained why that was a mistake, using case studies from recalls done by similar companies."). Then, talk about the results ("In the end, since we got ahead of negative press, this wound up being a PR win.