Paul Thompson (Joseph Fiennes) is a writer who lost his wife and child a few years back. He and his best friend, Jeff (Justin Kirk), have talked about swimming the length of the Hudson River since they were kids. Paul asks Jeff to come along with him on his trip to finally swim the river. Jeff agrees and brings along one of his friends, Liz (Elizabeth Reaser). Paul is determined to reach the end of the river by a certain date, August 28.