Just repeating what someone else has said on here.
Contrary to what has been said, if you have had your save game overwritten when trying to play Episode 4, it is not lost!
Copy your save file from slot 1 into slot 3. Then choose slot 1 to play with and select Episode 4. When you start playing you should see your previous decisions play out.
It worked for me so I hope it works for all. If you have more than 1 save then all I know is this works for your game in slot 1.
Thanks go to the person who originally posted this and NO THANKS to Telltale games for seemingly ignoring all the customers with this same problem and falsely advising them their save data is lost.