Exit the door and make your way to the fountain, being careful not to be seen by the witch.
Note: Strategically walk behind the shrubs to hide, being sure to stand in the middle space of the shrub. If you are caught by Nora T. Hagg you will need to repeat the process involving the magnet and the mouse. (Do not try to surge, it will likely result in being spotted.)
Check the fountain for a key.
Return east down the shrubs to the shed, being careful not to be caught by the witch, and use the key on the door.
Try to take the ball, the experiment will appear and attack you.