Report Offensive Message
Agree with Chip
I haven't had to do this a lot (limited consulting experience), but it has come up. Be up front, honest and communicate. Maybe try to wrap up the work you have done in such a way that it shows what value you have added to the process and makes it easier for the next person to take over. I think if you can show that the money they spent wasn't wasted that will go a long way for future work.