What happens if the people you buy a house from arent moved out on the possesion date?

We bought a house in a small town 6 months ago. Our possession date is tomorrow. It doesn't look like the people we bought from are making much of an effort to move out. They have built a house in another town and its complete but they aren't moving yet. Now they may have hired movers or are just moving tomorrow but I was curious what happens if they don't move out. Do we have any recourse if he doesn't move out everything? We both used the same real estate agent.