Agatha Christie: Peril at Endhouse

I am stuck on a level. I have finished the level and it still goes back to the same one.

Your obvious first move is to get out of the game, close down your computer, and start up again.

If that doesn't work, try uninstalling and reinstalling the game. If you're worried--as I would be!--that you will then lose your progress so far, call Big Fish support for help in that process.