I think Im just as lost as you are whenever you do it the first time you use Expecto Patronum then whenever you try the second time your camera stay on the lake. Im pretty sure you have to use the map to get passed it but its hard b/c I keep getting stuck in one spot. Sorry if this didnt help... XoXo

you have to use a spell something expecto patronam to use that spell you have to get that out of one of the books and when you have learned that spell it will tell you what botton you have to press to say it.